RFR: GitLab approval support missing asString

[Robin Westberg]

This minor fix makes the approval button support for GitLab work properly.

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Commit messages:
 - Fix missing asString

Changes: https://git.openjdk.java.net/skara/pull/941/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=941&range=00
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/941.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/941/head:pull/941

PR: https://git.openjdk.java.net/skara/pull/941