fix(tree-select): fixed error for test unit

commitlint.config.js

@@ -38,6 +38,7 @@ module.exports = {
                 'toggle',
                 'tooltip',
                 'tree',
+                'tree-select',
                 'typography',
                 'visual'
             ]

src/lib/tree-select/tree-select.component.ts

@@ -837,7 +837,7 @@ export class McTreeSelect extends McTreeSelectMixinBase implements
             event.preventDefault();
 
             this.open();
-        } else if (!this.multiple) {
+        } else if (!this.multiple && this.tree.keyManager && this.tree.keyManager.onKeydown) {
             this.tree.keyManager.onKeydown(event);
         }
     }