fix(ssr): remove redundant SVG attributes with undefined value

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Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

#18381 set some required metadata for SVG elements but it didn't skip the undefined values, which caused the chart to generate many redundant attributes with the 'undefined' value.

In this PR, I add a precheck for dataIndex. It will skip to set SSR data if the dataIndex is not present.

Also, I fixed an unexpected assignment:

- childECData.ssrType === 'chart';
+ childECData.ssrType = 'chart';

Besides, I also added a non-null check in zrender. Please refer to ecomfe/zrender#1048.

Fixed issues

#18381

Comparison

Before	After

Document Info

One of the following should be checked.

• This PR doesn't relate to document changes
• The document should be updated later
• The document changes have been made in apache/echarts-doc#xxx

Misc

ZRender Changes

• This PR depends on ZRender changes (ecomfe/zrender#xxx).

Related test cases or examples to use the new APIs

Please refer to test/svg-ssr.html.

Others

Merging options

• Please squash the commits into a single one when merging.

Other information

[echarts-bot]

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[github-actions]

The changes brought by this PR can be previewed at: https://echarts.apache.org/examples/editor?version=PR-19461@7a26ce5&renderer=svg

[Ovilia]

Thanks for the help! ;)

[echarts-bot]

Congratulations! Your PR has been merged. Thanks for your contribution! 👍