Reset filtering of incident list by selecting no filter

[johannaengland]

When reviewing #1122 I found what I first assumed was a bug in that PR, but turns out the React frontend acts the same way.

When I have already selected a filter and the select no filter (------- in the list) I would want the filtering to be reset and everything to be shown instead of the results of the previous filter.

Screenshot:

I would describe this as a request and not a bug since it still is clearly indicated that the list is filtered by the conditions that the previous filter has.