Fix Bin::getElementByInterface<T>() to use dynamicCast to cast to the interface.
Fix Bin::getElementByInterface<T>() to use dynamicCast to cast to the interface.

ylatuya/qt-gstreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer,dejunk/gstreamer,cyndis/qtgstreamer,tswindell/qt-gstreamer,cyndis/qtgstreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer,knuesel/qt-gstreamer,shadeslayer/qtgstreamer,comicfans/libqtgstreamer,detrout/qt-gstreamer,GStreamer/qt-gstreamer,shadeslayer/qtgstreamer,detrout/qt-gstreamer,nasserGanjali/QtGStreamer,knuesel/qt-gstreamer,comicfans/libqtgstreamer,iperry/qt-gstreamer,GStreamer/qt-gstreamer,detrout/qt-gstreamer,comicfans/libqtgstreamer,GStreamer/qt-gstreamer,knuesel/qt-gstreamer,iperry/qt-gstreamer,iperry/qt-gstreamer,tswindell/qt-gstreamer,cyndis/qtgstreamer,ylatuya/qt-gstreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer,nasserGanjali/QtGStreamer,ylatuya/qt-gstreamer,dejunk/gstreamer,nasserGanjali/QtGStreamer,tswindell/qt-gstreamer,shadeslayer/qtgstreamer,dejunk/gstreamer