mtmd : fix 32-bit narrowing issue in export-lora and mtmd clip (#14503)

* [fix] Fix 32-bit narrowing issue in export-lora and mtmd clip

* Update export-lora.cpp

* Update clip.cpp

* Update export-lora.cpp

* format: use space to replace tab

tools/export-lora/export-lora.cpp

@@ -148,7 +148,7 @@ struct lora_merge_ctx {
 
         ctx_out = gguf_init_empty();
         struct ggml_init_params params = {
-            /*.mem_size   =*/ gguf_get_n_tensors(base_model.ctx_gguf)*ggml_tensor_overhead(),
+            /*.mem_size   =*/ static_cast<size_t>(gguf_get_n_tensors(base_model.ctx_gguf)*ggml_tensor_overhead()),
             /*.mem_buffer =*/ NULL,
             /*.no_alloc   =*/ true,
         };

tools/mtmd/clip.cpp

@@ -2315,7 +2315,7 @@ struct clip_model_loader {
 
         // create data context
         struct ggml_init_params params = {
-            /*.mem_size =*/ (gguf_get_n_tensors(ctx_gguf.get()) + 1) * ggml_tensor_overhead(),
+            /*.mem_size =*/ static_cast<size_t>(gguf_get_n_tensors(ctx_gguf.get()) + 1) * ggml_tensor_overhead(),
             /*.mem_buffer =*/ NULL,
             /*.no_alloc =*/ true,
         };