search-tool: Check directory existence more carefully

Handle nullptr explicitly to prevent a GLib-CRITICAL runtime error.

Author: radioactiveman

src/search-tool/search-tool.cc

@@ -99,7 +99,7 @@ static String get_uri ()
         return strstr (path1, "://") ? path1 : to_uri (path1);
 
     const char * path2 = g_get_user_special_dir (G_USER_DIRECTORY_MUSIC);
-    if (g_file_test (path2, G_FILE_TEST_EXISTS))
+    if (path2 && g_file_test (path2, G_FILE_TEST_EXISTS))
         return to_uri (path2);
 
     return to_uri (g_get_home_dir ());