RFR: 8347562: javac crash due to type vars in permits clause

[Hannes Greule]

This fix ignores erroneous types when attributing permits clauses. Before, multiple erroneous types would lead to an exception in the duplication check. Additionally, such types would cause package mismatch errors. As javac already reports errors before, such an additional error is more confusing than helpful.

Note that there are additional type var checks, but those only apply if the type vars come from a type other than the type with the permits clause, i.e. an enclosing class.

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Commit messages:
 - fix

Changes: https://git.openjdk.org/jdk/pull/23069/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23069&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347562
  Stats: 15 lines in 3 files changed: 14 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23069.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23069/head:pull/23069

PR: https://git.openjdk.org/jdk/pull/23069