md-step not working with v-for

[lishichao1002]

Steps to reproduce

<button @click="steps.push(1)">add step</button>
<md-steppers>
        <md-step :md-label="'a'" v-for="(step, index) in steps" :id="index">
          error on click 
        </md-step>
      </md-steppers>

vue.esm.js?efeb:628 [Vue warn]: Error in v-on handler: "TypeError: Cannot set property 'done' of undefined"

found in

---> <MdStepperHeader> at src/components/MdSteppers/MdStepHeader.vue
       <MdStep> at src/components/MdSteppers/MdStep.vue
         <MdSteppers> at src/components/MdSteppers/MdSteppers.vue
           <Addcases> at src/pages/cases/addcases.vue
             <MdContent> at src/components/MdContent/MdContent.vue
               <MdAppContent> at src/components/MdApp/MdAppContent.vue
                 <MdAppSideDrawer> at src/components/MdApp/MdAppSideDrawer.vue
                   <App> at src/App.vue
                     <Root>
warn @ vue.esm.js?efeb:628
logError @ vue.esm.js?efeb:1893
globalHandleError @ vue.esm.js?efeb:1888
handleError @ vue.esm.js?efeb:1848
invokeWithErrorHandling @ vue.esm.js?efeb:1871
invoker @ vue.esm.js?efeb:2188
original._wrapper @ vue.esm.js?efeb:7559
vue.esm.js?efeb:1897 TypeError: Cannot set property 'done' of undefined
    at VueComponent.setStepperAsDone (vue-material.js?2e0c:11902)
    at VueComponent.setPreviousStepperAsDone (vue-material.js?2e0c:11909)
    at VueComponent.setActiveStep (vue-material.js?2e0c:11918)
    at click (vue-material.js?2e0c:32321)
    at invokeWithErrorHandling (vue.esm.js?efeb:1863)
    at HTMLButtonElement.invoker (vue.esm.js?efeb:2188)
    at HTMLButtonElement.original._wrapper (vue.esm.js?efeb:7559)

Which browser?

macos chrome latest

What is expected?

What is actually happening?

Reproduction Link