Revert "Better to use deleteLater with QObjects."

This reverts commit 3ec80be2a1.

This was causing a crash when changing filesystem (reformatting).

src/core/operationstack.cpp

@@ -456,7 +456,7 @@ void OperationStack::clearOperations()
         Operation* o = operations().takeLast();
         if (o->status() == Operation::StatusPending)
             o->undo();
-        o->deleteLater();
+        delete o;
     }
 
     emit operationsChanged();