error: forward declaration of 'const class QMimeData'

[glixx]

src/mainviewer.cpp: In member function 'virtual void MainViewer::dragEnterEvent(QDragEnterEvent*)':
src/mainviewer.cpp:525:26: error: invalid use of incomplete type 'const class QMimeData'
     if (event->mimeData()->hasFormat("application/x-mutationpreviewwidget")
                          ^
In file included from /usr/lib/qt5/include/QtWidgets/QGraphicsSceneMouseEvent:1:0,
                 from src/mainviewer.cpp:25:
/usr/lib/qt5/include/QtWidgets/qgraphicssceneevent.h:50:7: error: forward declaration of 'const class QMimeData'
 class QMimeData;
       ^
src/mainviewer.cpp:526:22: error: invalid use of incomplete type 'const class QMimeData'
  || event->mimeData()->hasFormat("application/x-qabstractitemmodeldatalist"))
                      ^
In file included from /usr/lib/qt5/include/QtWidgets/QGraphicsSceneMouseEvent:1:0,
                 from src/mainviewer.cpp:25:
/usr/lib/qt5/include/QtWidgets/qgraphicssceneevent.h:50:7: error: forward declaration of 'const class QMimeData'
 class QMimeData;
       ^
src/mainviewer.cpp: In member function 'virtual void MainViewer::dropEvent(QDropEvent*)':
src/mainviewer.cpp:534:23: error: invalid use of incomplete type 'const class QMimeData'
  if (event->mimeData()->hasFormat("application/x-qabstractitemmodeldatalist"))
                       ^
In file included from /usr/lib/qt5/include/QtWidgets/QGraphicsSceneMouseEvent:1:0,
                 from src/mainviewer.cpp:25:
/usr/lib/qt5/include/QtWidgets/qgraphicssceneevent.h:50:7: error: forward declaration of 'const class QMimeData'
 class QMimeData;
       ^
src/mainviewer.cpp:536:30: error: invalid use of incomplete type 'const class QMimeData'
   int idx = event->mimeData()->data("application/x-qabstractitemmodeldatalist").toInt();
                              ^
In file included from /usr/lib/qt5/include/QtWidgets/QGraphicsSceneMouseEvent:1:0,
                 from src/mainviewer.cpp:25:
/usr/lib/qt5/include/QtWidgets/qgraphicssceneevent.h:50:7: error: forward declaration of 'const class QMimeData'
 class QMimeData;
       ^
src/mainviewer.cpp:545:28: error: invalid use of incomplete type 'const class QMimeData'
  else if (event->mimeData()->hasFormat("application/x-mutationpreviewwidget"))
                            ^
In file included from /usr/lib/qt5/include/QtWidgets/QGraphicsSceneMouseEvent:1:0,
                 from src/mainviewer.cpp:25:
/usr/lib/qt5/include/QtWidgets/qgraphicssceneevent.h:50:7: error: forward declaration of 'const class QMimeData'
 class QMimeData;
       ^
Makefile:12112: recipe for target '.obj/mainviewer.o' failed

[glixx]

Fixed.