fixed from PVS-Studio

V773 The function was exited without releasing the 'mmfile' pointer. A memory leak is possible. load_abc.cpp 441

third_party/libmodplug/src/load_abc.cpp

@@ -438,6 +438,7 @@ static MMFILE *mmfopen(const char *name, const char *mode)
 		mmfile = (MMFILE *)malloc(len+sizeof(MMFILE));
 	if( !mmfile || len <= 0 ) {
 		fclose(fp);
+		free(mmfile);
 		return NULL;
 	}
 	fseek(fp, 0, SEEK_SET);