Skip ready functions if not in main thread or plugins are not loaded yet

InvenTree/label/apps.py

@@ -12,7 +12,8 @@ from django.conf import settings
 from django.core.exceptions import AppRegistryNotReady
 from django.db.utils import OperationalError
 
-from InvenTree.ready import canAppAccessDatabase
+from InvenTree.ready import (canAppAccessDatabase, isInMainThread,
+                             isPluginRegistryLoaded)
 
 logger = logging.getLogger("inventree")
 
@@ -35,6 +36,10 @@ class LabelConfig(AppConfig):
 
     def ready(self):
         """This function is called whenever the label app is loaded."""
+        # skip loading if plugins are not loaded or we run in a background thread
+        if not isPluginRegistryLoaded() or not isInMainThread():
+            return
+
         if canAppAccessDatabase():
 
             try: