Clear musicWriteBlob after writing BinaryMusic.vvv

Since musicWriteBlob is a temporary object that gets destroyed at the
end of musicclass::init(), in order to make sure we don't leak memory
and lose all the pointers to the blocks we just allocated in
musicWriteBlob, we need to call its clear() method after writing
BinaryMusic.vvv.

desktop_version/src/Music.cpp

@@ -69,6 +69,7 @@ void musicclass::init()
 #undef FOREACH_TRACK
 
 	musicWriteBlob.writeBinaryBlob("data/BinaryMusic.vvv");
+	musicWriteBlob.clear();
 #endif
 
 	num_mmmmmm_tracks = 0;