remove unused event

src/app/debugger/debuggerUI/VmDebugger.js

@@ -127,7 +127,7 @@ function VmDebugger (_parentUI, _traceManager, _codeManager, _solidityProxy, _ca
     })
   })
 
-  this.stepDetail = new StepDetail(_parentUI, _traceManager)
+  this.stepDetail = new StepDetail()
   _parentUI.debugger.event.register('traceUnloaded', this, function () {
     self.stepDetail.reset()
   })

src/app/debugger/debuggerUI/vmDebugger/StepDetail.js

-'use strict'
 var yo = require('yo-yo')
 var DropdownPanel = require('./DropdownPanel')
 
 function StepDetail (_parentUI, _traceManager) {
-  this.debugger = _parentUI.debugger
-  this.parentUI = _parentUI
-  this.traceManager = _traceManager
-
   this.basicPanel = new DropdownPanel('Step detail', {json: true, displayContentOnly: true})
 
   this.detail = {