QC may crash when editing doc interferes mouse based modifications

Steps to reproduce:

• open a Quick / QML based app
• open a qml file / ui.qml file
• add some components and a connection from one to another
• switch view to the integrated qml editor (not the Edit mode)
• remove the connection and save
• connections list still shows the respective connection
• remove it by selecting it and hit the '-' button

Current result:

• QC crashes