Demangle should not crash if out_size is 0.

Co-authored-by: Sergiu Deitsch <[email protected]>

Author: martonka

src/demangle.cc

@@ -1350,9 +1350,11 @@ bool Demangle(const char* mangled, char* out, size_t out_size) {
     return false;
   }
 
-  size_t copy_size = std::min(n, out_size);
-  std::copy_n(unmangled.get(), copy_size, out);
-  out[copy_size - 1] = '\0'; // Ensure terminating null if n > out_size
+  if (out_size > 0) {
+    std::size_t copy_size = std::min(n, out_size - 1);
+    std::copy_n(unmangled.get(), copy_size, out);
+    out[copy_size] = '\0'; // Ensure terminating null if n > out_size
+  }
   return status == 0;
 #else
   State state;