winealsa.drv: Initialize correctly the header before adding it to the queue.

dlls/winealsa.drv/midi.c

@@ -578,7 +578,10 @@ static DWORD midAddBuffer(WORD wDevID, LPMIDIHDR lpMidiHdr, DWORD dwSize)
     if (!(lpMidiHdr->dwFlags & MHDR_PREPARED)) return MIDIERR_UNPREPARED;
 
     EnterCriticalSection(&crit_sect);
+    lpMidiHdr->dwFlags &= ~WHDR_DONE;
     lpMidiHdr->dwFlags |= MHDR_INQUEUE;
+    lpMidiHdr->dwBytesRecorded = 0;
+    lpMidiHdr->lpNext = 0;
     if (MidiInDev[wDevID].lpQueueHdr == 0) {
 	MidiInDev[wDevID].lpQueueHdr = lpMidiHdr;
     } else {