Fix null checks in _BundleWriterReferences.

Change-Id: I9c99f62846cbc574e1a4694c5b4bb18c578ab6e2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/189422
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

https://dart.googlesource.com/sdk/+/637d4f84076faecbbf87c03e943a1bdce2ebe93f
1 file changed
tree: e60ba2af105e91cdc868f45d7e49e287d5fd33a8
  1. commits.json