Fix: decoder crash when --AML=0 and --IBC=1.

The encoder is supposed to check the high-level AML enable flag before calling the reordering function (that is adjustIBCMergeCandidates), but it is not in the ECM SW. Because the decoders always checks the flag before performing reordering, an implementation-wise mismatch between encoder and decoder is thus caused, resulting in decoding crash. The fix is provided at the encoder to follow the decoder design.