fix: Fix RLPReader overflow bug

Author: QEDK

contracts/lib/RLPReader.sol

@@ -333,12 +333,15 @@ library RLPReader {
             dest += WORD_SIZE;
         }
 
+        if (len == 0) return;
+
         // left over bytes. Mask is used to remove unwanted bytes from the word
         uint mask = 256 ** (WORD_SIZE - len) - 1;
+
         assembly {
             let srcpart := and(mload(src), not(mask)) // zero out src
             let destpart := and(mload(dest), mask) // retrieve the bytes
             mstore(dest, or(destpart, srcpart))
         }
     }
-}
+}