toaster: projectpage Disable/Enable build input if we have 0 layers

If we've removed all the layers in the configuration, disable the build
button and build input.

Signed-off-by: Michael Wood <michael.g.wood@intel.com>
Signed-off-by: Elliot Smith <elliot.smith@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

lib/toaster/toastergui/static/js/projectpage.js

@@ -175,11 +175,18 @@ function projectPageInit(ctx) {
 
   function updateLayersCount(){
     var count = $("#layers-in-project-list").children().length;
+    var noLayerMsg = $("#no-layers-in-project");
+    var buildInput = $("#build-input");
 
-    if (count === 0)
+
+    if (count === 0) {
+      noLayerMsg.fadeIn();
       $("#no-layers-in-project").fadeIn();
-    else
-      $("#no-layers-in-project").hide();
+      buildInput.attr("disabled", "disabled");
+    } else {
+      noLayerMsg.hide();
+      buildInput.removeAttr("disabled");
+    }
 
     $("#project-layers-count").text(count);