Fix crash when failing to open log file for writing

(cherry picked from commit 7a5d61816c95c64a905e46480ffec3a5af880a5a)

core/io/logger.cpp

@@ -166,6 +166,7 @@ void RotatedFileLogger::rotate_file() {
 	}
 
 	file = FileAccess::open(base_path, FileAccess::WRITE);
+	ERR_FAIL_COND_MSG(file.is_null(), "Failed to open log file for writing: " + base_path);
 	file->detach_from_objectdb(); // Note: This FileAccess instance will exist longer than ObjectDB, therefore can't be registered in ObjectDB.
 }