"Select a collection..." dropdown on dataset returns 400

[max-zilla]

https://clowder.ncsa.illinois.edu/clowder/datasets/5e398b4f5e0e2b6b85510821

URL that is called when the dropdown is clicked has incorrect parameter mapping: https://clowder.ncsa.illinois.edu/clowder/api/collections/datasetPossibleParents/undefined?when=5e398b4f5e0e2b6b85510821&date=5

(note that ?when= contains the dataset ID)

[robkooper]

I wonder if this is the same as https://github.com/clowder-framework/clowder/pull/275/files

[max-zilla]

#345