Angularjs 使用角度材质md自动完成时出错

我正在使用角度材质自动完成。单击“自动完成”文本框时出错

TypeError: Cannot read property 'then' of undefined
at me (angular-material.min.js:13)
at ve (angular-material.min.js:13)
at e.q [as focus] (angular-material.min.js:13)
at fn (eval at compile (angular.js:15152), <anonymous>:4:295)
at e (angular.js:26673)
at b.$eval (angular.js:17958)
at b.$apply (angular.js:18058)
at HTMLInputElement.<anonymous> (angular.js:26678)
at HTMLInputElement.dispatch (jquery.min.js:3)
at HTMLInputElement.r.handle (jquery.min.js:3)

这是我的html

<md-content layout-padding layout="column">
        <form ng-submit="$event.preventDefault()">

            <md-autocomplete ng-disabled="ctrl.isDisabled"
                             md-no-cache="ctrl.noCache"
                             md-selected-item="ctrl.selectedItem"
                             md-search-text-change="ctrl.searchTextChange(ctrl.searchText)"
                             md-search-text="ctrl.searchText"
                             md-selected-item-change="ctrl.selectedItemChange(item)"
                             md-items="item in ctrl.querySearch(ctrl.searchText)"
                             md-item-text="item.name"
                             md-min-length="0"
                             placeholder="Pick an Angular repository"
                             md-menu-class="autocomplete-custom-template">
                <md-item-template>
                    <span class="item-title">
                        <md-icon md-svg-icon="img/icons/octicon-repo.svg"></md-icon>
                        <span> {{item.name}} </span>
                    </span>
                    <span class="item-metadata">
                        <span class="item-metastat">
                            <strong>{{item.watchers}}</strong> watchers
                        </span>
                        <span class="item-metastat">
                            <strong>{{item.forks}}</strong> forks
                        </span>
                    </span>
                </md-item-template>
            </md-autocomplete>
        </form>
    </md-content>

{{item.name}
{{item.watchers}}观察者
{{item.forks}forks

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我无法跟踪此错误。请帮助。

您没有实例化所选项目

self.selectedItem = [];

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我已经写了var self=this；self.selectedItem=[]；仍然不起作用。同样的错误。

self.selectedItem = [];