Plugins: Don't fail if plugins dir does not exist

gajim/plugins/helpers.py

@@ -127,5 +127,7 @@ def get_builder(file_name: str, widgets: List[str] = None) -> Builder:
 
 def is_shipped_plugin(path):
     base = Path(configpaths.get('PLUGINS_BASE'))
+    if not base.exists():
+        return False
     plugin_parent = Path(path).parent
     return base.samefile(plugin_parent)