Fixed segfault when reshaping edge through the label
Merge branch 'master' of github.com:qreal/qreal into robots

Conflicts:
	qrgui/umllib/label.cpp
Fixed segfault when removing explosion source and target sequentially;
Fixed segfault when undoing global action;
== Id() replaced with .isNull() // TODO: replace != Id()
Merge branch 'master' of github.com:qreal/qreal into robots
Removed auto-replaced whitespaces before .isNull()
Merge pull request #963 from dvvrd/robots

Unregistered critical fixes