Merge pull request #1738 from rachel-fenichel/bugfix/1484

Create an empty pattern if there is no grid.

core/grid.js

@@ -219,6 +219,9 @@ Blockly.Grid.createDom = function(rnd, gridOptions, defs) {
           {'stroke': gridOptions['colour']}, gridPattern);
     }
     // x1, y1, x1, x2 properties will be set later in update.
+  } else {
+    // Edge 16 doesn't handle empty patterns
+    Blockly.utils.createSvgElement('line', {}, gridPattern);
   }
   return gridPattern;
 };