https://bugs.kde.org/show_bug.cgi?id=416013#c5

Followup to commit 21c34d60 fix for crash on moving element in diagram,
> Break the recursive event loop in UMLScene::mouseMoveEvent().

umbrello/umlscene.cpp function mouseMoveEvent
- Apparently the recursive loop is not limited to pre Qt5 versions.
  Remove #if QT_VERSION < 0x050000 preprocessor guard, i.e  make the
  previously #if dependent code unconditional. Remove #else part.

CCBUG: 416013