[Fixed Position] Modify fixed position to use the Selection API

Change method name to shouldSelect() as requested by the reviewer.

Fix tests.

Fixes #1848

platform/commonUI/regions/src/InspectorController.js

@@ -50,7 +50,11 @@ define(
                         view.show(container);
                     } else {
                         self.providerView = false;
-                        $scope.inspectorKey = selection[0].context.oldItem.getCapability("type").typeDef.inspector;
+                        var selectedItem = selection[0].context.oldItem;
+
+                        if (selectedItem) {
+                            $scope.inspectorKey = selectedItem.getCapability("type").typeDef.inspector;
+                        }
                     }
                 }