fr-process: Fix memory leak

Fixes Clang static analyzer warning:

fr-process.c:740:3: warning: Potential leak of memory pointed to by 'argv'
                g_warning ("The files could not be move: %s\n", commandline);
                ^~~~~~~~~

src/fr-process.c

@@ -735,10 +735,8 @@ start_current_command (FrProcess *process)
	}
#endif

	if ((fixname) && (system(commandline) != 0)) {
	if ((fixname) && (system(commandline) != 0))
		g_warning ("The files could not be move: %s\n", commandline);
		return;
	}

	if (info->begin_func != NULL)
		(*info->begin_func) (info->begin_data);