add metadata button is back

[tcnichol]

fixes the missing metadata button.

[ddey2]

looks good

[tcnichol]

The metadata button was missing since setEnableAddMetadata should not have been added to the conditional for the button. It starts false and will be set to true by the button.

[longshuicy]

After I created some user metadata and then click "add metadata" it leads me to a blank page

[tcnichol]

@longshuicy

I have not been able to replicate the blank screen after add metadata.

I tried to replicate the same situation - metadata type abstract and metadata text field, but it worked for me and the new metadata was added to the dataset.

[tcnichol]

I am able to replicate the blank screen error. Working to fix.

[tcnichol]

I think I fixed the empty screen problem after clicking add metadata.

datasetRole !== undefined works
datasetRole.role !== undefined does not, since you can't get .role from undefined.