message: fix(model): fix array index binding for v-model checkbox
  Closes
diff: @@ -86,8 +86,8 @@ function genCheckboxModel (
  'if(Array.isArray($$a)){' +
  `var $$v=${number ? '_n(' + valueBinding + ')' : valueBinding},` +
  '$$i=_i($$a,$$v);' +
  - `if($$el.checked){$$i<0&&(${value}=$$a.concat([$$v]))}` +
  - `else{$$i>-1&&(${value}=$$a.slice(0,$$i).concat($$a.slice($$i+1)))}` +
  + `if($$el.checked){$$i<0&&(${genAssignmentCode(value, '$$a.concat([$$v])')})}` +
  + `else{$$i>-1&&(${genAssignmentCode(value, '$$a.slice(0,$$i).concat($$a.slice($$i+1))')})}` +
  `}else{${genAssignmentCode(value, '$$c')}}`,
  null, true
  )
  