[clang-tidy] Fix an assertion failure in misc-redundant-expression.

Summary:
The assertion "isIntegerConstantExpr" is triggered in the
isIntegerConstantExpr(), we should not call it if the expression is value
dependent.

Reviewers: gribozavr

Subscribers: xazax.hun, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D62947

llvm-svn: 362701