Several extensions trigger custom actions. Make sure, those actions are
only performed, if airline is actually active and not temporarily
disabled using e.g. :AirlineToggle
Fix: a literal '0' appears after filename on older versions of vim-lsp.
0c8164b1b3 added support for showing lsp
progress, but didn't always explicitly return a value. Vim uses 0 as a
return value when none are supplied, so when used with an older version
of vim-lsp that doesn't have the progress feature a 0 appeared in the
statusline.
