variation of `causal2.js` raises incorrect causality error.

[florence]

The following program:

"require hopscript"
let hh = require("hiphop");
let inSig = {accessibility: hh.IN};
let outSig = {accessibility: hh.OUT};
let prg =  <hh.module>
        <hh.local V_S_C>
      <hh.sequence>
       <hh.if V_S_C><hh.nothing/> <hh.nothing/>
       </hh.if>
       <hh.local V_S_i>
         <hh.if V_S_i><hh.emit V_S_C/><hh.nothing/></hh.if>
       </hh.local>
      </hh.sequence>
    </hh.local>
  </hh.module>;
let machine = new hh.ReactiveMachine(prg, "prog")
machine.react()

reports a causality cycle between V_S_i and V_S_C. However there should be no cycle, because V_S_i is never emitted, which should let us determine that V_S_C is also absent.

This program is basically the same as causal2.js but V_S_i is declared after the first conditional, not before.