Unit tests fail with issue: The null object does not have a method '[]'.

[akserg]

Chrome 39.0.2171 (Linux 0.0.0) [TooltipComponent] should not be open initially FAILED
Test failed: Caught The null object does not have a method '[]'.

NoSuchMethodError: method not found: '[]'
Receiver: null
Arguments: [447006108]
#0      Object._noSuchMethod (dart:core-patch/object_patch.dart:42)
#1      Object.noSuchMethod (dart:core-patch/object_patch.dart:45)
#2      EventTarget._removeEventListener (dart:html:17308)
#3      EventTarget.removeEventListener (dart:html:17259)
#4      TooltipBase.unregisterTriggers (package:angular_ui/tooltip/tooltip.dart:407:14)
#5      TooltipBase.scope=.<anonymous closure> (package:angular_ui/tooltip/tooltip.dart:198:7)
#6      NodeAttrs.observe (package:angular/core_dom/directive.dart:60:15)
#7      TooltipBase.scope= (package:angular_ui/tooltip/tooltip.dart:197:12)