Sort Uniques by Visit does not work on some portals

[SebastianHelm]

This occurs when using the Uniques add-on. Some portals, such as https://www.ingress.com/intel?ll=50.182744,8.486106&z=17&pll=50.182744,8.486106, don't get sorted by the Visit column.

Repro:

1. Select a view that includes https://www.ingress.com/intel?ll=50.182744,8.486106&z=17&pll=50.182744,8.486106 and a few portals around it. E.g. this view: https://www.ingress.com/intel?ll=50.182744,8.486106&z=17&pll=50.182744,8.486106.
2. Select Portals list.
3. Click on the "Visit" heading.

Expected:

All portals should be sorted by their visit (and capture) status.

Observed:

Portals are sorted in the following sequence:

1. Not visited
2. Visited only
3. Visited+Captured
4. Again some portals that have not been visited

Expected:

Unvisited portals to be sorted together.

Fix:

In uniques.user.js, at the end of function uniqueValue(guid), add the following line:
return 0;