Possible memory leak in function readCard

[pit-nrw]

In function readCard is a possible memory leak, caused by removing of a modifier card.
When a modifier card is removed, only the activeModifier is set to null, but the memory is not freed.

TonUINO/Tonuino.ino

Lines 1635 to 1642 in 73b5681

	if (tempCard.nfcFolderSettings.folder == 0) {
	if (activeModifier != NULL) {
	if (activeModifier->getActive() == tempCard.nfcFolderSettings.mode) {
	activeModifier = NULL;
	Serial.println(F("modifier removed"));
	if (isPlaying()) {
	mp3.playAdvertisement(261);
	}

Should be fixed by using:
delete activeModifier;

Or the implementation of Modifier class could be changed to contain a destructor which gets called.

[AlexanderWillner]

What about a pull request? I'd merge it into my branch.