(GH-320) Handle @param tags for non-existent params

[h4l]

Fixes #320

Classes and defined types with docstring @param tags for parameters that are not actually present in the parameter list cause the language server to crash, due to populate_classes_from_yard_registry assuming param tags always have a :types array present.

@param tags without types are now ignored. Note that class/defined type parameters without a specified type automatically have the "Any" type in their :types array, so they're not excluded by this change.

[CLAassistant]

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[h4l]

Cool, pleased to help!