Fix resetting oparg on exception

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/nodes/bytecode/PBytecodeRootNode.java

@@ -1439,6 +1439,7 @@ Object executeFromBci(VirtualFrame virtualFrame, Frame localFrame, Frame stackFr
                     // to be replaced with the exception
                     stackFrame.setObject(stackTop, pe);
                     bci = decodeBCI((int) newTarget);
+                    oparg = 0;
                 }
             }
         }