Update ReedSolomonDecoder.php

Fix exception use error.

Author: xiabeifeng

lib/Common/Reedsolomon/ReedSolomonDecoder.php

@@ -132,7 +132,7 @@ private function runEuclideanAlgorithm($a, $b, $R)
             $t = $q->multiply($tLast)->addOrSubtract($tLastLast);
 
             if ($r->getDegree() >= $rLast->getDegree()) {
-                throw new IllegalStateException("Division algorithm failed to reduce polynomial?");
+                throw new ReedSolomonException("Division algorithm failed to reduce polynomial?");
             }
         }