Merge pull request #5556 from dearblue/setidx

Fix typo for `OP_SETIDX`

src/vm.c

@@ -1273,7 +1273,7 @@ RETRY_TRY_BLOCK:
     }
 
     CASE(OP_SETIDX, B) {
-      c = 1;
+      c = 2;
       mid = MRB_OPSYM(aset);
       goto L_SEND_SYM;
     }