basetexteditor/qmljseditor: fix destructor problem

solve problems depending on the destructor sequence:
- avoid setting code style to a destroyed code style
- avoid hiding a potentially destroyed pane
  (which will be cleared in any case)

Task-number: QTCREATORBUG-8818
Change-Id: Idd7817d99bf4ff04c5e152b00857f6e35825fd37
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/qmljseditor/qmljseditor.cpp

@@ -532,7 +532,6 @@ QmlJSTextEditorWidget::QmlJSTextEditorWidget(QWidget *parent) :
 
 QmlJSTextEditorWidget::~QmlJSTextEditorWidget()
 {
-    hideContextPane();
     m_semanticInfoUpdater->abort();
     m_semanticInfoUpdater->wait();
 }

src/plugins/texteditor/basetexteditor.cpp

@@ -4614,9 +4614,12 @@ void BaseTextEditorWidget::onCodeStylePreferencesDestroyed()
 {
     if (sender() != d->m_codeStylePreferences)
         return;
+    ICodeStylePreferences *prefs = TextEditorSettings::instance()->codeStyle(languageSettingsId());
+    if (prefs == d->m_codeStylePreferences)
+        prefs = 0;
     // avoid failing disconnects, m_codeStylePreferences has already been reduced to QObject
     d->m_codeStylePreferences = 0;
-    setCodeStyle(TextEditorSettings::instance()->codeStyle(languageSettingsId()));
+    setCodeStyle(prefs);
 }
 
 void BaseTextEditorWidget::slotCodeStyleSettingsChanged(const QVariant &)