[clang-tidy] Fixed readability-else-after-return for cascade statements

Summary:
Fix generated by this check changed program semantics
in the case where 'if' was a part (direct child) of other statement.

Fixes PR30652.

Patch by Paweł Żukowski.

Reviewers: malcolm.parsons, alexfh, djasper

Subscribers: mgehre, omtcyfz, cfe-commits

Differential Revision: https://reviews.llvm.org/D26125

llvm-svn: 285999