Fixed possible crash in pck_packer.cpp due to wrong memory freeing.

core/io/pck_packer.cpp

@@ -175,7 +175,7 @@ Error PCKPacker::flush(bool p_verbose) {
 		printf("\n");
 
 	file->close();
-	memdelete(buf);
+	memdelete_arr(buf);
 
 	return OK;
 };