llama: initialize pre-norm embedding mask flag (#23256)

src/llama-context.cpp

@@ -66,6 +66,7 @@ llama_context::llama_context(
     cparams.yarn_beta_slow   = params.yarn_beta_slow   >= 0.0f ? params.yarn_beta_slow   : hparams.yarn_beta_slow;
     cparams.embeddings                  = params.embeddings;
     cparams.embeddings_pre_norm         = false;
+    cparams.embeddings_pre_norm_masked  = false;
     cparams.offload_kqv      = params.offload_kqv;
     cparams.no_perf          = params.no_perf;
     cparams.pooling_type     = params.pooling_type;