B4R Library MD_MAX72XX Led-Matrix Library

Looks great!!!

Hello,
I have a problem to make it work on a Wemos Mini D1.
It had worked with the example at the begin but now, the card reset always with an exception.
EDIT Solved: -> Maybe the electric consumption with the led's matrix is too high, it seems the ESP are really sensitive to that.
I haven't any documentation for this Led matrix, someone know where i can find something ? Or have any idea how many mA/A to make it work with 4, or even 1 module ?
-> No, if ever you met this problem search for Null pointer !
The problem was the doc. of lib say that we pass a 'Null' to reset the default font, it's not good. Don't do that, it's why i had an exception because the 'Null' pointer, ESP don't like that !
So, now i need to find how i can put and use the default font or another.
Any idea ?

Thank you