fix issue with database path falling back to faulty path

update logic in welcome wizard, add checks for qapplication instance

config/config.py

@@ -1,4 +1,4 @@
-from typing import Optional, Any
+from typing import Optional, Any, Union
 from dataclasses import dataclass
 from omegaconf import OmegaConf, DictConfig
 import os
@@ -31,8 +31,8 @@ class Zotero:
 @dataclass
 class Database:
     name: str
-    path: str | Path
-    temp: str | Path
+    path: Union[str, Path, None]
+    temp: Union[str, Path, None]
     def getattr(self, name: str):
         return getattr(self, name)