fasta: revert check for null fileUri in the error reporting of the verifier.
fasta: revert check for null fileUri in the error reporting of the verifier.

(as discussed in https://codereview.chromium.org/2894283002, we are reverting
this because we don't know how to reproduce this issue anymore. When it comes up
again we can either fix the issue or re-revert and include an explanation).

R=ahe@google.com

Review-Url: https://codereview.chromium.org/2902153003 .

dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk