[C++] Fix union copy constructor to work with nested structs (#6552) (#6607)
[C++] Fix union copy constructor to work with nested structs (#6552) (#6607)


google/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,google/flatbuffers,google/flatbuffers,evolutional/flatbuffers,google/flatbuffers,evolutional/flatbuffers,google/flatbuffers,alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,google/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,google/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,google/flatbuffers,evolutional/flatbuffers,google/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,google/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,alexames/flatbuffers