Compilation warning becomes an error with esp32

[fabianoriccardi]

Hi everyone,
while I was compiling the example on ESP32-Arduino (updated to the latest version), I got the following error:

C:\Users\fabiu\workspace_arduino\libraries\MFRC522-I2C-Library-master\MFRC522_I2C.cpp: In member function 'byte MFRC522::PCD_CommunicateWithPICC(byte, byte, byte*, byte, byte*, byte*, byte*, byte, bool)':

C:\Users\fabiu\workspace_arduino\libraries\MFRC522-I2C-Library-master\MFRC522_I2C.cpp:451:20: error: '_validBits' may be used uninitialized in this function [-Werror=maybe-uninitialized]

   if (*backLen < 2 || _validBits != 0) {

                    ^

cc1plus.exe: some warnings being treated as errors

It's very eary to solve, you can set _validBits to 0 in the definition. Could you integrated the modification in the "official" code?