fix: double free when getting command path for empty command

```
minishell$ ""
```
leads to the following error:
```
=================================================================
==1158770==ERROR: AddressSanitizer: attempting double-free on 0x5060000020c0 in thread T0:
    #0 0x5649fcb5b8a8 in free.part.0 asan_malloc_linux.cpp.o
    #1 0x5649fcbac549 in deal_with_filled_path /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:119:3
    #2 0x5649fcbac38b in filepath_from_env /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:165:10
    #3 0x5649fcbac220 in get_cmdpath /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:186:10
    #4 0x5649fcba8664 in simple_cmd_execute /home/khais/src/42/common_env/minishell/src/executing/simple_cmd/simple_cmd_execute.c:71:8
    #5 0x5649fcba6e4c in execute_command /home/khais/src/42/common_env/minishell/src/minishell.c:49:2
    #6 0x5649fcba6ce5 in main /home/khais/src/42/common_env/minishell/src/minishell.c:92:3
    #7 0x7fb4f2dcd27d in __libc_start_call_main (/nix/store/nqb2ns2d1lahnd5ncwmn6k84qfd7vx2k-glibc-2.40-36/lib/libc.so.6+0x2a27d) (BuildId: 704cab5816f130c494208e8cc24d87a386ef085b)
    #8 0x7fb4f2dcd338 in __libc_start_main@GLIBC_2.2.5 (/nix/store/nqb2ns2d1lahnd5ncwmn6k84qfd7vx2k-glibc-2.40-36/lib/libc.so.6+0x2a338) (BuildId: 704cab5816f130c494208e8cc24d87a386ef085b)
    #9 0x5649fca6f394 in _start (/home/khais/src/42/common_env/minishell/minishell+0x2b394)

0x5060000020c0 is located 0 bytes inside of 58-byte region [0x5060000020c0,0x5060000020fa)
freed by thread T0 here:
    #0 0x5649fcb5b8a8 in free.part.0 asan_malloc_linux.cpp.o
    #1 0x5649fcbac669 in select_path /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:81:3
    #2 0x5649fcbac524 in deal_with_filled_path /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:116:9
    #3 0x5649fcbac38b in filepath_from_env /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:165:10
    #4 0x5649fcbac220 in get_cmdpath /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:186:10
    #5 0x5649fcba8664 in simple_cmd_execute /home/khais/src/42/common_env/minishell/src/executing/simple_cmd/simple_cmd_execute.c:71:8
    #6 0x5649fcba6e4c in execute_command /home/khais/src/42/common_env/minishell/src/minishell.c:49:2
    #7 0x5649fcba6ce5 in main /home/khais/src/42/common_env/minishell/src/minishell.c:92:3
    #8 0x7fb4f2dcd27d in __libc_start_call_main (/nix/store/nqb2ns2d1lahnd5ncwmn6k84qfd7vx2k-glibc-2.40-36/lib/libc.so.6+0x2a27d) (BuildId: 704cab5816f130c494208e8cc24d87a386ef085b)

previously allocated by thread T0 here:
    #0 0x5649fcb5c897 in malloc (/home/khais/src/42/common_env/minishell/minishell+0x118897)
    #1 0x5649fcbac6be in alloc_path /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp_utils.c:34:9
    #2 0x5649fcbac4e9 in deal_with_filled_path /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:113:15
    #3 0x5649fcbac38b in filepath_from_env /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:165:10
    #4 0x5649fcbac220 in get_cmdpath /home/khais/src/42/common_env/minishell/src/subst/simple_filename_exp.c:186:10
    #5 0x5649fcba8664 in simple_cmd_execute /home/khais/src/42/common_env/minishell/src/executing/simple_cmd/simple_cmd_execute.c:71:8
    #6 0x5649fcba6e4c in execute_command /home/khais/src/42/common_env/minishell/src/minishell.c:49:2
    #7 0x5649fcba6ce5 in main /home/khais/src/42/common_env/minishell/src/minishell.c:92:3
    #8 0x7fb4f2dcd27d in __libc_start_call_main (/nix/store/nqb2ns2d1lahnd5ncwmn6k84qfd7vx2k-glibc-2.40-36/lib/libc.so.6+0x2a27d) (BuildId: 704cab5816f130c494208e8cc24d87a386ef085b)

SUMMARY: AddressSanitizer: double-free asan_malloc_linux.cpp.o in free.part.0
==1158770==ABORTING
```

Looks like select_path frees filepath sometimes, no idea why. Removing these
lines didn't break any tests.

I'm pushing this to get a second opinion

src/executing/simple_cmd/simple_cmd_execute.c

@@ -6,7 +6,7 @@
 /*   By: khais <marvin@42.fr>                       +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2025/03/27 16:21:56 by khais             #+#    #+#             */
-/*   Updated: 2025/04/01 16:37:31 by khais            ###   ########.fr       */
+/*   Updated: 2025/04/01 18:08:02 by khais            ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
@@ -17,6 +17,8 @@
 #include "../../env/env_convert.h"
 #include <unistd.h>
 #include <sys/wait.h>
+#include <stdio.h>
+#include "../../subst/path_split.h"
 
 static char	**argv_from_wordlist(t_wordlist *wordlist)
 {
@@ -39,6 +41,24 @@ static void	command_not_found(t_simple_cmd *cmd)
 		cmd->words->word->word);
 }
 
+static void	ft_execve(char *exe, char **argv, char **envp)
+{
+	execve(exe, argv, envp);
+	ft_dprintf(STDERR_FILENO, "minishell: %s: ", argv[0]);
+	perror(NULL);
+	free(exe);
+	path_split_destroy(argv);
+	path_split_destroy(envp);
+}
+
+static void	execute_subprocess(char *exe, t_simple_cmd *cmd, t_minishell *app)
+{
+	ft_execve(exe, argv_from_wordlist(cmd->words), envp_from_env(app->env));
+	simple_cmd_destroy(cmd);
+	env_destroy(app->env);
+	exit(127);
+}
+
 void	simple_cmd_execute(t_simple_cmd *cmd, t_minishell *app)
 {
 	char	*exe;
@@ -56,7 +76,7 @@ void	simple_cmd_execute(t_simple_cmd *cmd, t_minishell *app)
 	}
 	pid = fork();
 	if (pid == 0)
-		execve(exe, argv_from_wordlist(cmd->words), envp_from_env(app->env));
+		execute_subprocess(exe, cmd, app);
 	free(exe);
 	waitpid(pid, NULL, 0);
 	return ;

src/subst/simple_filename_exp.c

@@ -6,7 +6,7 @@
 /*   By: khais <marvin@42.fr>                       +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2025/03/02 13:40:10 by jguelen           #+#    #+#             */
-/*   Updated: 2025/03/27 18:39:23 by khais            ###   ########.fr       */
+/*   Updated: 2025/04/01 18:38:35 by khais            ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
@@ -77,8 +77,6 @@ static char	*select_path(char *filepath, char **oldpath, char **path,
 		else
 			return (free(*oldpath), path_split_destroy(path), filepath);
 	}
-	if (*oldpath != filepath)
-		free(filepath);
 	return (NULL);
 }
 

test.sh

@@ -335,6 +335,13 @@ status=1
 hello=hi
 EOF
 
+when_run <<EOF "empty command is not found"
+""
+EOF
+expecting <<EOF
+minishell: : command not found
+EOF
+
 when_run <<EOF "quoted parentheses are not operators"
 echo unclosed '('
 EOF