walk-exprs handler fn is called for var forms regardless of predicate

[immoh]

This is also causing macroexpand-all to fail with NPE (handler fn is nil) for all forms containing var forms:

user=> (riddley.walk/macroexpand-all '(var riddley.walk/macroexpand-all))
NullPointerException   riddley.walk/walk-exprs/fn--1323 (walk.clj:202)

This was introduced in ced3fa5 which also adds a test that relies on the fact that handler fn gets called even though predicate is constantly false.

I wasn't sure how to fix this. Do you also expect macroexpand-all to return var values instead of var forms?

[ztellman]

I just need to add a predicate check to that condition, I think.