Hides randomize button overlay, resolves #1409

app/styles/editor/level/thangs_tab.sass

@@ -216,20 +216,12 @@ $mobile: 1050px
     #canvas-wrapper
       width: 100%
       position: relative
-
-      #canvas-overlay
-        display: none
+      text-align: center
+      
+      #randomize-button
         position: absolute
-        width: 100%
-        height: 100%
-        background: white
-        opacity: 0.5
-        text-align: center
-
-        #randomize-button
-          position: absolute
-          top: 45%
-          height: 40px
+        top: 45%
+        height: 40px
 
 
   

app/templates/editor/level/thangs_tab.jade

@@ -25,8 +25,7 @@ button.navbar-toggle.toggle.btn-primary#thangs-palette-toggle(type="button", dat
 .world-container.thangs-column
   h3(data-i18n="editor.level_tab_thangs_conditions") Starting Conditions
   #canvas-wrapper
-    #canvas-overlay
-      button.btn.btn-primary(id="randomize-button", data-toggle="coco-modal", data-target="editor/level/modals/TerrainRandomizeModal", data-i18n="editor.randomize", title="Randomize Terrain") Randomize
+    button.btn.btn-primary(id="randomize-button", data-toggle="coco-modal", data-target="editor/level/modals/TerrainRandomizeModal", data-i18n="editor.randomize", title="Randomize Terrain") Randomize
     ul.dropdown-menu#contextmenu
       li#delete
         a(data-i18n="editor.delete") Delete

app/views/editor/level/thangs/ThangsTabView.coffee

@@ -157,6 +157,8 @@ module.exports = class ThangsTabView extends CocoView
     thangsHeaderHeight = $('#thangs-header').height()
     oldHeight = $('#thangs-list').height()
     $('#thangs-list').height(oldHeight - thangsHeaderHeight)
+    if data.thangs.length
+      @$el.find('#randomize-button').hide()    
 
   initSurface: ->
     surfaceCanvas = $('canvas#surface', @$el)
@@ -235,7 +237,6 @@ module.exports = class ThangsTabView extends CocoView
       @addThang @addThangType, thang.pos, true
     @batchInsert()
     @selectAddThangType null
-    @$el.find('#canvas-overlay').css('display', 'none')
 
 
   # TODO: figure out a good way to have all Surface clicks and Treema clicks just proxy in one direction, so we can maintain only one way of handling selection and deletion
@@ -410,6 +411,7 @@ module.exports = class ThangsTabView extends CocoView
     @thangsBatch = []
 
   addThang: (thangType, pos, batchInsert=false) ->
+    @$el.find('#randomize-button').hide()
     if batchInsert
       thangID = "Random #{thangType.get('name')} #{@thangsBatch.length}"
     else