SEARCHDATA_FILE (searchdata.xml) keyword elements blank

[neilsimon]

Describe the bug
The searchdata.xml keyword elements are empty when it is generated with external search enabled.

Expected behavior
The keyword elements should contain keywords.

To Reproduce

1. Run cmake thus: cmake -Dbuild_search=ON.
2. Run make.
3. Edit Doxyfile and change EXTERNAL_SEARCH to YES.
4. Run bin/doxygen Doxyfile.
5. Verify that there are no keywords in the generated searchdata.xml file: grep keywords doxygen_docs/searchdata.xml.
6. Check out Release_1_9_1 and do the same noting that there are keywords in the searchdata.xml file.

Version
Versions 1.9.3 and master are affected. Version 1.9.1 and 1.8.20 are not.

[albert-github]

I've just pushed a proposed patch, pull request #9033

[albert-github]

Code has been integrated in master on GitHub (please don't close the issue as this will be done at the moment of an official release).

[doxygen]

This issue was previously marked 'fixed but not released',
which means it should be fixed in doxygen version 1.9.4.
Please verify if this is indeed the case. Reopen the
issue if you think it is not fixed and please include any additional information
that you think can be relevant (preferably in the form of a self-contained example).