ToolButtons not usable when switching too fast from Editor to Designer and back

Steps to reproduce:

• create or open a QtQuick 2 application
• open one of the views at the botton (Compile Output, General Messages,...) (this step could be skipped)
• open a QML file
• type <Ctrl+3>, <Ctrl+2> (fast, so that the warning mentioned in QTCREATORBUG-7858 appears on Edit mode instead of Design mode)

Current behaviour:

• if you had one view opened at the bottom: this view is now grey
• if you hit the ToolButton(s) to switch between the views at the bottom - nothing happens (if you switch now to Debug/Analyze/... they seem to get re-initialized and are usable again on Edit mode too)