[Dark mode] Text in the navbar search is dark under FireFox

[chalin]

Originally posted by @fekete-robert in #1896 (comment)

When using a dark system theme under firefox the text in the navbar search is dark (tested on mac and linux):

Using Brave (a chrome derivative) it's fine on both systems.

But this is probably an edge case, since firefox has a marginal market share, so we can consider it a known issue and go forward.