[trunk regression] Images in score should be resizable

Steps to reproduce bug
1. Drag an image file onto a score
2. Double click the image

Expected behavior: The image should show a blue handle for resizing the image

Actual behavior: The image appears unresponsive to double clicks (and unresponsive to right clicks too)

MuseScore version: r. 5106 nightly (image resizing works in MuseScore 1.1 stable)

(Operating System: Windows 7)