Added explicit fallback to default soundfont

With no soundfonts found the game crashed on startup
Local UNIX build had the same issue because $PROGDIR/soundfonts is not in search path

src/sound/i_soundfont.cpp

@@ -372,6 +372,11 @@ void FSoundFontManager::CollectSoundfonts()
 			}
 		}
 	}
+
+	if (soundfonts.Size() == 0)
+	{
+		ProcessOneFile(NicePath("$PROGDIR/soundfonts/gzdoom.sf2"));
+	}
 }
 
 //==========================================================================

src/sound/mididevices/music_fluidsynth_mididevice.cpp

@@ -324,10 +324,7 @@ FluidSynthMIDIDevice::FluidSynthMIDIDevice(const char *args)
 	{
 		return;
 	}
-	if (LoadPatchSets(nullptr))
-	{
-		return;
-	}
+
 	// The following will only be used if no soundfont at all is provided, i.e. even the standard one coming with GZDoom is missing.
 #ifdef __unix__
 	// This is the standard location on Ubuntu.

src/version.h

@@ -97,7 +97,6 @@ const char *GetVersionString();
 #define GAMESIG "GZDOOM"
 #define BASEWAD "gzdoom.pk3"
 #define OPTIONALWAD "zd_extra.pk3"
-#define BASESF "gzdoom.sf2"
 
 // More stuff that needs to be different for derivatives.
 #define GAMENAME "GZDoom"