The wrong value was used here.

This caused crashes on some files (notably MBELLS from Cosmo and NUBC
from Body Count) in my port of this code to SLADE 3.

src/oplsynth/opl_mus_player.cpp

@@ -267,7 +267,7 @@ bool OPLmusicBlock::ServiceStream (void *buff, int numbytes)
 					{
 						for (i = 0; i < io->NumChips; ++i)
 						{
-							io->chips[i]->Update(samples1, samplesleft);
+							io->chips[i]->Update(samples1, numsamples);
 						}
 						OffsetSamples(samples1, numsamples << stereoshift);
 					}