Fix decryption bug

weather-sensor/firmware/encryption.c

 
 		/* Setup for next block */
 		currentCipherBlock = previousCipherBlock;
-		if (previousCipherBlock != (uint8_t*) data)
+		if (previousCipherBlock != (uint8_t*) data + LENGTH_OF_BLOCK)
 		{
 			previousCipherBlock -= LENGTH_OF_BLOCK;
 		}