Fix JVET_Y0065_GPM_INTRA with NAMVP and interaction with SIGN_PREDICTION (off)
NAMVP candidates do not check if neighboring block is inter and not intra since GPM_INTRA
When SIGN_PREDICTION is off, GPM_INTRA causes decoding mismatch.
NAMVP candidates do not check if neighboring block is inter and not intra since GPM_INTRA
When SIGN_PREDICTION is off, GPM_INTRA causes decoding mismatch.