Fix KeyError when using backend-specific updates formatter
Fix KeyError when using backend-specific updates formatter

When a backend-specific formatter (i.e. ``{Pacman}``, ``{Cower}``, etc.)
is used, and the initial "working" status is set, the loop in which the
update totals is compiled has not yet run, leading to a KeyError.

This commit fixes the traceback by setting initial values of "?" for
these formatters before the initial "working" status is set.

eBrnd/i3pystatus,ncoop/i3pystatus,drwahl/i3pystatus,asmikhailov/i3pystatus,drwahl/i3pystatus,facetoe/i3pystatus,Arvedui/i3pystatus,facetoe/i3pystatus,richese/i3pystatus,m45t3r/i3pystatus,eBrnd/i3pystatus,fmarchenko/i3pystatus,yang-ling/i3pystatus,fmarchenko/i3pystatus,richese/i3pystatus,schroeji/i3pystatus,enkore/i3pystatus,ncoop/i3pystatus,yang-ling/i3pystatus,teto/i3pystatus,Arvedui/i3pystatus,asmikhailov/i3pystatus,enkore/i3pystatus,teto/i3pystatus,schroeji/i3pystatus,m45t3r/i3pystatus