Themes Plugin internal error 500 with solr search provider

[HeatherHillers]

(tenantConfig.json attached)

Add a solr search configuration as a search provider for a theme and configure it by directly editing tenantConfig.json.

Open QWC Admin and generate the configuration.

Restart the browser

Check the Theme in the website and confirm that the search is configured and running properly, so the configuration is definitely good.

Open QWC Admin.
Open Themes

Attempt to load the Theme Configuration form for the project configured for the search provider.

You will get a 500 error. It will only happen for the project with the solr search provider.

Presumably, this could be because the Project form has an entry for search providers, and it doesn't support more than simple search provider names, while solr has a more complicated config.

.#
'''
"searchProviders": [
"coordinates",
"nominatim",
{
"provider": "solr",
"default": [
"Gemeinden"
],
"layers": {
}
}
],

[tenantConfig.zip](https://github.com/qwc-services/qwc-admin-gui/files/8061190/tenantConfig.zip)