[clang-tidy] Fix another crash in make-unique check.

Summary:
The crash happens when calling `reset` method without any preceding
operation like "->" or ".", this could happen in a subclass of the
"std::unique_ptr".

Reviewers: alexfh

Reviewed By: alexfh

Subscribers: JDevlieghere, xazax.hun, cfe-commits

Differential Revision: https://reviews.llvm.org/D36452

llvm-svn: 310496