Fix some leftover issues

This PR fixes a number of issues

Items with empty "RelatedTo" values were rejected when the form content was loaded from a file due to incorrect type check.
Arrays of "RelatedTo" values were not handled when loading form content from a file
Numeric values were stored as strings in MBDB JSONs.
Tristate value type overlapped with string, leading to unexpected results when logic depended on the result of the corresponding type checks
Values of custom components are set as "Not provided" when input MBDB data does not contain any data for the corresponding custom component

Molecular-Biophysics-Database / mbdb-input-ui