Small fixes.

dexed_sysex.cpp

@@ -223,13 +223,13 @@ bool load_sysex(uint8_t b, uint8_t v, uint8_t instance_id)
 #if DEBUG
   bool found = false;
 #endif
-  v %= MAX_VOICES;
+  v = constrain(v, 1, MAX_VOICES);
-  b %= MAX_BANKS;
+  b = constrain(b, 1, MAX_BANKS);
 
   if (sd_card_available)
   {
     File sysex;
-    char sysex_file_name[4 + VOICE_NAME_LEN];
+    char sysex_file_name[10 + VOICE_NAME_LEN];
     uint8_t data[128];
 
     create_sysex_filename(b, sysex_file_name, instance_id);