fix(#9361): appear error when using inline-template with no children

[kerm1it]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch for v2.x (or to a previous version branch), not the master branch
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md#development-setup
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

add a dev-only warning for inline-template with no children.

[kerm1it]

@posva

[posva]

You don't need to ping me like that. I'm already tracking activity in this repo 😄

[kerm1it]

You don't need to ping me like that. I'm already tracking activity in this repo 😄

Can you tell me why test-ssr-weex isn't passed?

[posva]

I actually don't know, I don't work on weex

[yyx990803]

Thanks for the PR, it is unnecessary to change files in packages because they are auto-generated. The only files that need to be modified are in src.

I've merged #9365 which fixes the same issue but has tests.