RFR: Fix two errors in recent commit

[Kelvin Nilsen]

1. An assert expression is missing class qualifier so code will not
   compile in debug mode
2. A minor spelling error in a comment

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Commit messages:
 - Fix two errors in recent commit

Changes: https://git.openjdk.java.net/shenandoah/pull/112/files
 Webrev: https://webrevs.openjdk.java.net/?repo=shenandoah&pr=112&range=00
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/shenandoah/pull/112.diff
  Fetch: git fetch https://git.openjdk.java.net/shenandoah pull/112/head:pull/112

PR: https://git.openjdk.java.net/shenandoah/pull/112