tdf#120807 check for valid ImplGetWindowImpl()

Change-Id: Ia1135d11990abc303849bd1b6a549c82008c79de
Reviewed-on: https://gerrit.libreoffice.org/62260
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>

vcl/source/window/winproc.cxx

@@ -1077,7 +1077,7 @@ static bool ImplHandleKey( vcl::Window* pWindow, MouseNotifyEvent nSVEvent,
     }
 
     // #105591# send keyinput to parent if we are a floating window and the key was not processed yet
-    if( !bRet && pWindow->ImplGetWindowImpl()->mbFloatWin && pWindow->GetParent() && (pWindow->ImplGetWindowImpl()->mpFrame != pWindow->GetParent()->ImplGetWindowImpl()->mpFrame) )
+    if( !bRet && pWindow->ImplGetWindowImpl() && pWindow->ImplGetWindowImpl()->mbFloatWin && pWindow->GetParent() && (pWindow->ImplGetWindowImpl()->mpFrame != pWindow->GetParent()->ImplGetWindowImpl()->mpFrame) )
     {
         pChild = pWindow->GetParent();