* Band-aid fixes:

- Fixed crash on startup in music_midi_out.cpp by preventing division by Tempo if Tempo is zero.
- Fixed crash on startup in gl_vertexbuffer.cpp when trying to access the sectors array though it was NULL. (It shouldn't even happen given numsectors is zero so the for iteration shouldn't even start, but it happened anyway for some mysterious reason.)
* Updated to ZDoom r2677:
- Cleaned up the ugly MIDI song creating code a little.
- Added a generic Standard MIDI File creator that works with any of the sequencers. mus2midi.cpp is no longer used but is kept around as a reference.
- Fixed: When the game nodes were the same as the render nodes, their pointers would not be NULLed.
- Renamed music_midi_midiout.cpp to music_smf_midiout.cpp.
- Moved MIDI precaching logic into MIDIStreamer so that SMF and HMI files can both use the same implementation.
- Added a player for HMI midi files.
- Set 'setslopeoverflow' compatibility flag for all maps in Massmouth2.

git-svn-id: http://mancubus.net/svn/hosted/gzdoom/trunk@932 b0f79afe-0144-0410-b225-9a4edf0717df

src/p_setup.cpp

@@ -3412,17 +3412,13 @@ void P_FreeLevelData ()
 		sectors = NULL;
 		numsectors = 0;	// needed for the pointer cleanup code
 	}
-	if (gamenodes && gamenodes!=nodes)
+	if (gamenodes != NULL && gamenodes != nodes)
 	{
-		delete [] gamenodes;
-		gamenodes = NULL;
-		numgamenodes = 0;
+		delete[] gamenodes;
 	}
-	if (gamesubsectors && gamesubsectors!=subsectors)
+	if (gamesubsectors != NULL && gamesubsectors != subsectors)
 	{
-		delete [] gamesubsectors;
-		gamesubsectors = NULL;
-		numgamesubsectors = 0;
+		delete[] gamesubsectors;
 	}
 	if (subsectors != NULL)
 	{
@@ -3434,13 +3430,15 @@ void P_FreeLevelData ()
 			}
 		}
 		delete[] subsectors;
-		subsectors = NULL;
 	}
 	if (nodes != NULL)
 	{
 		delete[] nodes;
-		nodes = NULL;
 	}
+	subsectors = gamesubsectors = NULL;
+	numsubsectors = numgamesubsectors = 0;
+	nodes = gamenodes = NULL;
+	numnodes = numgamenodes = 0;
 	if (lines != NULL)
 	{
 		delete[] lines;