Fix #slider in Dark theme
Fix #slider in Dark theme

See https://github.com/FreshRSS/FreshRSS/commit/6b560c61330b254e794057ef36515e4c751114f4
Fix https://github.com/FreshRSS/FreshRSS/issues/750

asmundg/FreshRSS,marienfressinaud/FreshRSS,samuelstein/FreshRSS,romibi/FreshRSS,romibi/FreshRSS,FreshRSS/FreshRSS,Alkarex/FreshRSS,Dolomich/FreshRSS,superboum/FreshRSS,aledeg/FreshRSS,asmundg/FreshRSS,aledeg/FreshRSS,Alkarex/FreshRSS,marienfressinaud/FreshRSS,Dolomich/FreshRSS,Alkarex/FreshRSS,FreshRSS/FreshRSS,FreshRSS/FreshRSS,romibi/FreshRSS,marienfressinaud/FreshRSS,aledeg/FreshRSS,aledeg/FreshRSS,asmundg/FreshRSS,superboum/FreshRSS,FreshRSS/FreshRSS,samuelstein/FreshRSS,Dolomich/FreshRSS,marienfressinaud/FreshRSS,Alkarex/FreshRSS,superboum/FreshRSS,romibi/FreshRSS,samuelstein/FreshRSS