Added call to [super updateConstraints] when no view controller could be found

The early return from the updateConstraints override when the map view isn't contained in a view controller (e.g. if it's embedded in a UIWindow) meant that the super class implementation wasn't being called (as per Apple's documentation: https://developer.apple.com/library/ios/documentation/uikit/reference/uiview_class/UIView/UIView.html#jumpTo_121), causing a crash.
Merge pull request #373 from markbeaton/patch-1

Added call to [super updateConstraints] when no view controller could be found