fix(uiGridHeader): Refresh grid with new header

In the case that the header template was arriving in a promise, the grid
was not refreshing the canvas and recalculating the header element height.

Fixes #2822

src/js/core/directives/ui-grid-header.js

@@ -51,6 +51,8 @@
                     containerCtrl.headerViewport = headerViewport;
                   }
                 }
+
+                $scope.grid.queueRefresh();
               });
 
             function updateHeaderReferences() {

src/js/core/factories/Grid.js

@@ -1967,11 +1967,11 @@ angular.module('ui.grid')
           container = containerHeadersToRecalc[i];
 
           // If this header's height is less than another header's height, then explicitly set it so they're the same and one isn't all offset and weird looking
-          if (container.headerHeight < maxHeaderHeight) {
+          if (maxHeaderHeight > 0 && typeof(container.headerHeight) !== 'undefined' && container.headerHeight !== null && container.headerHeight < maxHeaderHeight) {
             container.explicitHeaderHeight = maxHeaderHeight;
           }
 
-          if (container.headerCanvasHeight < maxHeaderCanvasHeight) {
+          if (typeof(container.headerCanvasHeight) !== 'undefined' && container.headerCanvasHeight !== null && maxHeaderCanvasHeight > 0 && container.headerCanvasHeight < maxHeaderCanvasHeight) {
             container.explicitHeaderCanvasHeight = maxHeaderCanvasHeight;
           }
         }