add check for root_type specified for json schema generation (#5622)
add check for root_type specified for json schema generation (#5622)


pjulien/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,google/flatbuffers,pjulien/flatbuffers,google/flatbuffers,pjulien/flatbuffers,google/flatbuffers,google/flatbuffers,google/flatbuffers,evolutional/flatbuffers,google/flatbuffers,google/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,DavadDi/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,pjulien/flatbuffers,pjulien/flatbuffers,google/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,pjulien/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,DavadDi/flatbuffers,alexames/flatbuffers,pjulien/flatbuffers,evolutional/flatbuffers,google/flatbuffers,pjulien/flatbuffers,google/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,pjulien/flatbuffers,google/flatbuffers,google/flatbuffers,DavadDi/flatbuffers,DavadDi/flatbuffers,evolutional/flatbuffers,pjulien/flatbuffers,google/flatbuffers,pjulien/flatbuffers,DavadDi/flatbuffers,alexames/flatbuffers,google/flatbuffers,alexames/flatbuffers,google/flatbuffers,pjulien/flatbuffers,DavadDi/flatbuffers