Fix condition-case empty success handler misinterpretation

Fix condition-case empty success handler misinterpretation

(condition-case X E (:success)) should return nil; the compiler
behaves correctly in this case.

* src/eval.c (internal_lisp_condition_case):
Evaluate an empty :success handler as nil instead of pretending it
isn't there.
* test/lisp/emacs-lisp/bytecomp-tests.el (bytecomp-tests--test-cases):
Add test case.