[lldb] Remove an assertion in RichManglingContext::GetBufferRef() hit when...

[lldb] Remove an assertion in RichManglingContext::GetBufferRef() hit when debugging a native x86 Windows process

Summary: A RichManglingContext constructed with an invalid demangled name or with a demangled function name without any context will have an empty context. This triggers an assertion in RichManglingContext::GetBufferRef() when debugging a native Windows process on x86 when it shouldn't. Remove the assertion.

Reviewers: aleksandr.urakov, zturner, lldb-commits

Reviewed By: zturner

Subscribers: erik.pilkington

Differential Revision: https://reviews.llvm.org/D52626

llvm-svn: 343292