9538: gramps.gen.dbstate.DbState.make_database doesn't handle 'else' branch

gramps/gen/dbstate.py

@@ -203,6 +203,7 @@ class DbState(Callback):
                 else:
                     self.save_modules()
             mod = pmgr.load_plugin(pdata)
+            if mod:
                 database = getattr(mod, pdata.databaseclass)
                 db = database()
                 import inspect
@@ -213,6 +214,10 @@ class DbState(Callback):
                              + (os.path.split(caller_frame[1])[1],)
                              + tuple(caller_frame[i] for i in range(2, 4))))
                 return db
+            else:
+                raise Exception("can't load database backend: '%s'" % plugin_id)
+        else:
+            raise Exception("no such database backend: '%s'" % plugin_id)
 
     def open_database(self, dbname, force_unlock=False, callback=None):
         """