dsound: Avoid division by zero when calculating Doppler shift.

dlls/dsound/sound3d.c

@@ -298,7 +298,8 @@ void DSOUND_Calc3DBuffer(IDirectSoundBufferImpl *dsb)
 	}
 	else if (!(dsb->ds3db_ds3db.vVelocity.x == dsb->device->ds3dl.vVelocity.x &&
 	           dsb->ds3db_ds3db.vVelocity.y == dsb->device->ds3dl.vVelocity.y &&
-	           dsb->ds3db_ds3db.vVelocity.z == dsb->device->ds3dl.vVelocity.z))
+	           dsb->ds3db_ds3db.vVelocity.z == dsb->device->ds3dl.vVelocity.z) &&
+	         !(vDistance.x == 0.0f && vDistance.y == 0.0f && vDistance.z == 0.0f))
 	{
 		/* calculate length of ds3db_ds3db.vVelocity component which causes Doppler Effect
 		   NOTE: if buffer moves TOWARDS the listener, its velocity component is NEGATIVE

dlls/dsound/tests/ds3d.c

@@ -1439,6 +1439,8 @@ static void test_doppler(GUID *guid, BOOL play)
     check_doppler(dsound, listener, play, DS3DMODE_NORMAL, 0, 0, 1, -90, 22050, 29400);
     check_doppler(dsound, listener, play, DS3DMODE_NORMAL, 0, 0, 1, 90, 22050, 17640);
 
+    check_doppler(dsound, listener, play, DS3DMODE_NORMAL, 0, 0, 0, -90, 22050, 22050);
+
     IDirectSound3DListener_Release(listener);
     ref = IDirectSoundBuffer_Release(primary);
     ok(!ref, "Got outstanding refcount %ld.\n", ref);