fix: add null pointer check for fopen call in ggml.c

- Add null check for fopen call in ggml_print_backtrace function
- Prevents null pointer dereference vulnerability

Addresses 2 null pointer dereference vulnerabilities (CWE-476)

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

Author: devin-ai-integration[bot]

ggml/src/ggml.c

@@ -137,6 +137,9 @@ void ggml_print_backtrace(void) {
     }
 #if defined(__linux__)
     FILE * f = fopen("/proc/self/status", "r");
+    if (f == NULL) {
+        return;
+    }
     size_t size = 0;
     char * line = NULL;
     ssize_t length = 0;