Crash when using CustomProtoMutator for multiple protos

[fmeum]

I have multiple protos that I need to mutate in a libFuzzer fuzz target and am thus calling CustomProtoMutator directly instead of using the macro. However, the Swap calls in the LastMutationCache crash when trying to swap out one proto for another:

[libprotobuf FATAL external/com_google_protobuf/src/google/protobuf/generated_message_reflection.cc:614] CHECK failed: (message2->GetReflection()) == (this): Second argument to Swap() (of type "some_proto") is not compatible with this reflection object (which is for type "some_other_proto"). Note that the exact same class is required; not just the same descriptor.

Patching out the cache resolved this issue. Would it be possible to either invalidate the cache if a new proto is mutated or add a way to disable the cache in CustomProtoMutator calls?