check for cells in assembly before moving to cam

css/main.css

@@ -211,7 +211,7 @@ hr {
 
 .inlineWarning {
     background-color: rgba(255,0,0,0.15);
-    padding: 10px 15px 15px 15px;
+    padding: 15px;
     margin: 0 0 20px 0;
 }
 

js/cam/cam.js

@@ -91,7 +91,7 @@ define(['underscore', 'three', 'backbone', 'appState', 'latticeCAM', 'threeModel
 
 
         _calculateNumMaterials: function(){//todo calc length of gik cells as separate material types
-            this.set("allCAMMaterialTypes", materials.getChildCellTypes(lattice.sparseCells, true));
+            this.set("allCAMMaterialTypes", materials.getChildCellTypes(lattice.sparseCells, true) || []);
         },
 
 

js/menus/templates/AssemblerMenuView.html

+<% if (numCells == 0){ %>
+    <div class="inlineWarning">No cells in assembly!</div>
+<% } %>
 Machine: &nbsp;&nbsp;
     <div class="btn-group">
         <button data-toggle="dropdown" class="btn dropdown-toggle" type="button"><%= allMachines[machineName].name %><span class="caret"></span></button>