Llama.cpp fixes zero divisor error in nemotron-h expert FFN size fallback.

The official source reports this update: b10947: models : guard the expert FFN size fallback in nemotron-h against a zero divisor. models : guard the expert FFN size fallback in nemotron-h against a zero divisor ( #28779 ) The NextN/MTP tail loop derives the expert FFN size as n_ff/n_expert_used when expert_feed_forward_length gives nothing for the layer. Both values come from per-layer arrays that legitimately hold 0 on layers that are not MoE, so a checkpoint whose predict layers hold 0 in both divides by zero and dies with SIGFPE at load time, with no error message. Report the malformed metadata instead.