LookupSelector cannot be cleared

[Brian Lewis]

Saw this in the context of special ed, but appears to be an intrinsic issue with the LookupSelector component:

once a value is saved, you cannot return to Null.

It appears that if the value is removed (ie you select the blank row in the dropdown list) then the value of the field becomes Undefined - not Null as expected. this undefined value is not part of the data packet that gets sent to the server on save, so the change is never saved on the server.

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[Brian Lewis]

An easier fix than expected, changing only the lookupselector template.

But as part of the move to Angular, we could consider replacing the LookupSelector coponent ( which exists to construct an md-select client-side) with an mvc HTML Helper, which could construct the md-select server-side. Then changing this helper would probably be simpler than building an Angular version of LookupSelector.

[Brian Lewis]

fix(lookups): Allow lookupselector with non-null value to be cleared

Resolves #815

→ <<cset e472c7642683>>