RFR: 8336389: Infinite loop occurs while resolving lookups [v2]

[John Hendrikx]

> Fixes an infinite loop that can occur while resolving lookups.
> 
> There were 2 bugs:
> - A `contains` check was done on some value X, but then a value Y was added to the set used to track duplicates
> - The `Set` to track duplicates was cleared in some recursive calls, meaning that the caller (which may be processing multiple values in a loop) would end up with an empty set, losing track of what was visited so far
> 
> Also removed a redundant `null` check (an NPE would have occurred before it could reach that code).

John Hendrikx has updated the pull request incrementally with one additional commit since the last revision:

  Fix formatting and spelling

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1505/files
  - new: https://git.openjdk.org/jfx/pull/1505/files/864ef9b2..5f949e32

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1505&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1505&range=00-01

  Stats: 27 lines in 1 file changed: 6 ins; 0 del; 21 mod
  Patch: https://git.openjdk.org/jfx/pull/1505.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1505/head:pull/1505

PR: https://git.openjdk.org/jfx/pull/1505