Error toggling child with multiple mixins

[coffeebite]

1. Describe your issue:

Say I have the following tag:

<parent>
  <child if="{showChild}"></child>
</parent>

If showChild resolves to true and then false, you get the following javascript error if the <child> tag has more than one mixin mixed in:

Cannot read property 'removeChild' of null

2. Can you reproduce the issue?
   With only one mixin (works): https://plnkr.co/edit/Qze8P2NSZcHDSEsJ1xc1
   With two mixins (doesn't work): https://plnkr.co/edit/FOjzXT7L2dxZGbLRu46l

3. On which browser/OS does the issue appear?
   Chrome/macOS Sierra

4. Which version of Riot does it affect?
   3.0.0

5. How would you tag this issue?

• Question
• Bug
• Discussion
• Feature request
• Tip
• Enhancement
• Performance

[GianlucaGuarini]

Thanks that's a bug