Disable ForestToParseTree cache when ambiguity='resolve'

[chanicpanic]

Fixes #1283.

[erezsh]

Lgtm.

I think maybe it's a good idea to add a comment explaining that caching is disabled because of the tree construction, or mention the issue number? Because it's not an obvious connection imho.

[chanicpanic]

I think maybe it's a good idea to add a comment explaining that caching is disabled because of the tree construction, or mention the issue number? Because it's not an obvious connection imho.

Good idea, added.

[erezsh]

Thanks!