Android: fix exception with non-existent default QtClipboardManager ctor

Don't call a non-existent default constructor for QtClipboardManager.
That throws the exception:

 java.lang.NoSuchMethodError: no non-static method "Lorg/qtproject/qt/
android/QtClipboardManager;.<init>()V"

Task-number: QTBUG-118077
Change-Id: I75d89446706895140ef54ccc2162436c55ef49b7
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

src/plugins/platforms/android/qandroidplatformclipboard.h

@@ -35,7 +35,7 @@ private:
     Q_DECLARE_JNI_NATIVE_METHOD_IN_CURRENT_SCOPE(onClipboardDataChanged)
 
     QMimeData *data = nullptr;
-    QtJniTypes::QtClipboardManager m_clipboardManager;
+    QtJniTypes::QtClipboardManager m_clipboardManager = nullptr;
 };
 
 QT_END_NAMESPACE