NPE in CompositeASTVisitor

[BoykoAlex]

No description provided.

[martinlippert]

I still think that the add method should have a @nonnull contract and null checks should happen before calling this method, but this is just a minor detail, so please go ahead with whatever you prefer.

[BoykoAlex]

I've explored returning Optional<ASTVisitor> for JDT reconciler and code action handlers... I have also noted that semantic token computations use the same CompositeASTVisitor API and would also need to switch to Optional<ASTVisitor> At this point in terms of changes adding a null check in the CompositeASTVisitor seemed like a good solution... Having an Optional return type rather than ASTVisitor seemed better than having null checks and jspecify annotations as it prevents this problem almost entirely. Maybe I'll revisit the Optional solution in conjunctions with @NonNull