Fixed Pointer Comparison Error in Lines 824 and 847 of MFRC522Extended

[vidura2]

Description of Changes:

Issue:
    The error occurred due to an incorrect comparison between a pointer (backLen) and an integer (0), leading to a compilation error. In C++, pointer comparisons should be done carefully to avoid unintended behavior. Specifically, comparing a pointer directly to an integer caused the following error:
        Error message: ordered comparison of pointer with integer zero ('byte*' {aka 'unsigned char*'} and 'int')
        This occurred on lines 824 and 847, where backLen was incorrectly compared as a pointer instead of properly checking its dereferenced value or using an appropriate condition.
Fix:
    Replaced the invalid comparison by ensuring the comparison is done correctly. The condition now checks the correct value type to avoid comparing a pointer to an integer. Specifically, the code was updated to check backData for null and backLen as an integer:

    cpp

    if (backData && backLen && (*backLen > 0)) {

    This ensures that the pointer is valid and that the value it points to is greater than 0, preventing the compilation error and ensuring correct behavior.

Impact of Changes:

Fixed compilation errors related to pointer comparisons.
Ensured proper handling of RFID communication data, which leads to improved stability in operations using the MFRC522Extended library.

[fpindej]

Would it be possible to get this one merged please? 🙏🏻 It seems to be generally known and re-occurring issue.

[vidura2]

just check my repo I have forked this repo