[24.0] Fix tool form building if select filters from unavailable dataset metadata

[mvdbeek]

Fixes:

Message
Uncaught exception in exposed API method:
Stack Trace(most recent call first)

TypeError: 'NoneType' object is not iterable
  File "galaxy/web/framework/decorators.py", line 346, in decorator
    rval = func(self, trans, *args, **kwargs)
  File "galaxy/webapps/galaxy/api/tools.py", line 247, in build
    return tool.to_json(trans, kwd.get("inputs", kwd), history=history)
  File "galaxy/tools/__init__.py", line 2509, in to_json
    populate_state(request_context, self.inputs, params.__dict__, state_inputs, state_errors)
  File "galaxy/tools/parameters/__init__.py", line 412, in populate_state
    _populate_state_legacy(
  File "galaxy/tools/parameters/__init__.py", line 525, in _populate_state_legacy
    state[input.name] = input.get_initial_value(request_context, context)
  File "galaxy/tools/parameters/basic.py", line 1107, in get_initial_value
    options = list(self.get_options(trans, other_values))
  File "galaxy/tools/parameters/basic.py", line 960, in get_options
    return self.options.get_options(trans, other_values)
  File "galaxy/tools/parameters/dynamic_options.py", line 893, in get_options
    rval = filter.filter_options(rval, trans, other_values)
  File "galaxy/tools/parameters/dynamic_options.py", line 227, in filter_options
    for r in ref:

from

https://sentry.galaxyproject.org/share/issue/ac3a350198604034aca07eaca3cc9cb8/

This happens if you have the following input section:

        <param name="otu" type="data" format="mothur.list,mothur.shared" label="list or shared - OTU List of Shared"/>
        <param name="repfasta" type="data" format="fasta" optional="true" label="repfasta - rep.fasta" help="rep.fasta file generated by get.oturep"/>
        <param name="label" type="select" label="label - OTU Labels" optional="true" help="Select exactly one label. If none selected, first label in your list or shared file will be used">
            <options>
                <filter type="data_meta" ref="otu" key="labels"/>
            </options>
        </param>

but there's no mothur.list or mothur.shared dataset in your history.

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.