fix(change_detector): add null check in _revertToPreviousState

mhbrown · chirayuk · commit 06435792a340 · 2015-03-31T15:43:42.000-07:00
Closes #1691
diff --git a/lib/change_detection/dirty_checking_change_detector.dart b/lib/change_detection/dirty_checking_change_detector.dart
@@ -1001,7 +1001,7 @@ class _CollectionChangeRecord<V> implements CollectionChangeRecord<V> {
       _linkedRecords.put(record);
     }
 
-    prev._next = null;
+    if (prev != null) prev._next = null;
     _itTail = prev;
     _undoDeltas();
   }

Original file line number	Diff line number	Diff line change
`@@ -1001,7 +1001,7 @@ class _CollectionChangeRecord<V> implements CollectionChangeRecord<V> {`
`1001`	`1001`	`_linkedRecords.put(record);`
`1002`	`1002`	`}`
`1003`	`1003`
`1004`		`- prev._next = null;`
	`1004`	`+ if (prev != null) prev._next = null;`
`1005`	`1005`	`_itTail = prev;`
`1006`	`1006`	`_undoDeltas();`
`1007`	`1007`	`}`