Fix: Correct pointer comparison issue in MFRC522Extended.cpp

- Fixed an issue in `MFRC522Extended.cpp` where the code incorrectly compared a pointer (`backLen`) with an integer.
- Modified the conditional statements at lines 824 and 847 to properly check if `backLen` is not null and its value is greater than zero.
- This resolves compilation errors related to ordered comparison of pointers with integers in the MFRC522 library.

Author: robosphere99

src/MFRC522Extended.cpp

@@ -821,7 +821,7 @@ MFRC522::StatusCode MFRC522Extended::TCL_Transceive(TagInfo *tag, byte *sendData
 	// Swap block number on success
 	tag->blockNumber = !tag->blockNumber;
 
-	if (backData && (backLen > 0)) {
+	if (backData && (*backLen > 0)) {
 		if (*backLen < in.inf.size)
 			return STATUS_NO_ROOM;
 
@@ -844,7 +844,7 @@ MFRC522::StatusCode MFRC522Extended::TCL_Transceive(TagInfo *tag, byte *sendData
 		if (result != STATUS_OK)
 			return result;
 
-		if (backData && (backLen > 0)) {
+		if (backData && (*backLen > 0)) {
 			if ((*backLen + ackDataSize) > totalBackLen)
 				return STATUS_NO_ROOM;