Creating a local EasyButton object results in callbacks to random adresses on memory

[mrroot165]

I think I found a bug:

Issue
If I create an Easybutton object as a global object, the libary works fine.
However, If I create it as a local object, it misbehaves badly:
The object sometimes performs callbacks to random adresses on the microcontrollers memory, when using EsayButton::read(), causign the programm to malfunction or crash.
This only happens sometimes and only if no callback function was used/specified.

Reason
I think I also found the issue causing this:
In EasyButtonBase.h, the callback function is specified like this:

class EasyButtonBase
{
...
#ifndef EASYBUTTON_DO_NOT_USE_SEQUENCES
    callback_t _pressed_sequence_callbacks[MAX_SEQUENCES];
#endif
    callback_t _pressed_callback;     // Callback function for pressed events.
    callback_t _pressed_for_callback; // Callback function for pressedFor events.

This results in the callbacks being initialized with 0 as the default value if being created as a global object. If created as a local object, they are not initialized and start with a random value.

In EasyButton.cpp it then checks if a callback is set by looking for non-zero values;

	if (_pressed_callback)
	{
		_pressed_callback();
	}

So If ther random starting value is not zero, this results in callbacks to random adresses.

Possible fix

Initialize the values properly:

#ifndef EASYBUTTON_DO_NOT_USE_SEQUENCES
    callback_t _pressed_sequence_callbacks[MAX_SEQUENCES] ={0};
#endif
    callback_t _pressed_callback = 0;     // Callback function for pressed events.
    callback_t _pressed_for_callback = 0; // Callback function for pressedFor events.