#183 ErrorList add TextArea extension on PropertiesChanged only

[Eric Le Lay]

Following [bugs:#4020], TextArea corruption was due to ErrorList ErrorHighlight extension constently being evicted because it threw in ExtensionManager#paintScreenLineRange and re-added on the next EditBus message.

So here is a patch to only listen to PropertiesChanged in this EBHandler method.
This is the last fix for #4020.

[Alan Ezust]

committed 24538