Check to see if these are empty before closing them.

If there is an error when creating the queue, currently it tries to close the queue but it can't because it doesn't exist. So check to see if it exists before closing it.

persistqueue/sqlbase.py

@@ -446,8 +446,10 @@ def _new_db_connection(self, path, multithreading, timeout
 
     def close(self) -> None:
         """Closes sqlite connections"""
-        self._getter.close()
-        self._putter.close()
+        if self._getter is not None:
+            self._getter.close()
+        if self._putter is not None:
+            self._putter.close()
 
     def __del__(self) -> None:
         """Handles sqlite connection when queue was deleted"""