fixed several -Wzero-as-null-pointer-constant warnings from gcc-15

Author: sezero

src/timidity/options.h

@@ -12,7 +12,7 @@
 /* When a patch file can't be opened, one of these extensions is
    appended to the filename and the open is tried again.
  */
-#define PATCH_EXT_LIST { ".pat", 0 }
+#define PATCH_EXT_LIST { ".pat", NULL }
 
 /* Acoustic Grand Piano seems to be the usual default instrument. */
 #define DEFAULT_PROGRAM 0

src/timidity/timidity.c

@@ -96,7 +96,7 @@ static int read_config_file(const char *name, int rcf_count)
         /* Originally the TiMidity++ extensions were prefixed like this */
     if (SDL_strcmp(w[0], "#extension") == 0)
     {
-        w[0]=SDL_strtok_r(0, " \t\240", &endp);
+        w[0]=SDL_strtok_r(NULL, " \t\240", &endp);
         if (!w[0]) continue;
     }