Fixed race condition in deferred link detection

When a label's text is updated while the deferred link detection is still in progress the app most likely crashes.

`detectedlinkLocations` would contain the text checking results of the previous text - not the current one. So it's text ranges are no longer valid which in turn leads to a crash when using them e.g. for applying link styles.

Also the new text wasn't link-checked automatically since the previous link detection was not yet complete.