Midi example should test for FW version prior to setting callbacks.

[TrackDaddy5]

• Arduino board: Mega 2560

• Arduino IDE version (found in Arduino -> About Arduino menu): PlatformIO - Visual Studio Code

• List the steps to reproduce the problem below (if possible attach a sketch or
  copy the sketch code in too): LIST REPRO STEPS BELOW

I have firmware version 0.6.7 on my BlueFruitLE. The callbacks in the MIDI example fails due the wrong FW version.

Putting this code prior to the callbacks would help for those debugging issues.

  if ( !ble.isVersionAtLeast(MINIMUM_FIRMWARE_VERSION) )
  {
    error( F("Callback requires at least 0.7.0") );
  }

[TrackDaddy5]

I've upgraded to 0.8.1 and everything runs great.