Comment inside of a template is treated as a string sometimes

[simplesmiler]

Vue.js version

1.0.22 to 1.0.24 (regression from 1.0.21)

Reproduction Link

1.0.22: https://jsfiddle.net/simplesmiler/bcga4gpk/
1.0.21: https://jsfiddle.net/simplesmiler/bcga4gpk/1/

What is Expected?

Comments are invisible.

What is actually happening?

Comments are visible sometimes. The trigger appears to be the absence of "solid" siblings (comments and text nodes are not "solid"), the comment appears to be treated as a text node.

[simplesmiler]

I'll give it a go this evening, should be fairly easy to fix.