libobs/util: Save filename in config_create

Fixes a bug where config_save could not save the file due to the fact
that it did not store the path of the file as it was supposed to.

libobs/util/config-file.c

@@ -70,6 +70,7 @@ config_t *config_create(const char *file)
 	fclose(f);
 
 	config = bzalloc(sizeof(struct config_data));
+	config->file = bstrdup(file);
 	return config;
 }