fix: add null pointer checks for fopen calls in vulkan-shaders-gen.cpp

- Add null checks for fopen calls in write_output_files function
- Prevents null pointer dereference vulnerabilities

Addresses 2 null pointer dereference vulnerabilities (CWE-476)

Co-Authored-By: Jake Cosme <[email protected]>

Author: devin-ai-integration[bot]

ggml/src/ggml-vulkan/vulkan-shaders/vulkan-shaders-gen.cpp

@@ -752,7 +752,16 @@ void process_shaders() {
 
 void write_output_files() {
     FILE* hdr = fopen(target_hpp.c_str(), "w");
+    if (hdr == nullptr) {
+        std::cerr << "Error opening header file: " << target_hpp << " (" << strerror(errno) << ")\n";
+        return;
+    }
     FILE* src = fopen(target_cpp.c_str(), "w");
+    if (src == nullptr) {
+        std::cerr << "Error opening source file: " << target_cpp << " (" << strerror(errno) << ")\n";
+        fclose(hdr);
+        return;
+    }
 
     fprintf(hdr, "#include <cstdint>\n\n");
     fprintf(src, "#include \"%s\"\n\n", basename(target_hpp).c_str());