Windows: Fix heap overflow setting native icon

Fixes #71697.

platform/windows/os_windows.cpp

@@ -3105,7 +3105,7 @@ void OS_Windows::set_native_icon(const String &p_filename) {
 	pos += sizeof(WORD);
 	f->seek(pos);
 
-	icon_dir = (ICONDIR *)memrealloc(icon_dir, 3 * sizeof(WORD) + icon_dir->idCount * sizeof(ICONDIRENTRY));
+	icon_dir = (ICONDIR *)memrealloc(icon_dir, sizeof(ICONDIR) + (icon_dir->idCount * sizeof(ICONDIRENTRY)));
 	f->get_buffer((uint8_t *)&icon_dir->idEntries[0], icon_dir->idCount * sizeof(ICONDIRENTRY));
 
 	int small_icon_index = -1; // Select 16x16 with largest color count