Avoid to create empty code style name

Change-Id: I6f81aebecdb137c79d8a0a3c7d429f46672c24a6
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/texteditor/codestyleselectorwidget.cpp

@@ -272,7 +272,7 @@ void CodeStyleSelectorWidget::slotCopyClicked()
                                                   QLineEdit::Normal,
                                                   tr("%1 (Copy)").arg(currentPreferences->displayName()),
                                                   &ok);
-    if (!ok)
+    if (!ok || newName.trimmed().isEmpty())
         return;
     ICodeStylePreferences *copy = codeStylePool->cloneCodeStyle(currentPreferences);
     if (copy) {