Don't fail if logger is not defined
Don't fail if logger is not defined

Introduced in a recent commit, a feed would be marked as "failed" if the logger is not defined (nil) when the feed content hasn't changed (304 Not Modified).

wwwjfy/stringer,adscott/stringer,swanson/stringer,Koronen/stringer,jqr/stringer,mpraglowski/stringer,dperson/stringer,lodestone/stringer,nibble/stringer,milligramme/stringer,run-project/stringer,milligramme/stringer,jeroenj/stringer,InPermutation/stringer,lodestone/stringer,run-project/stringer,lodestone/stringer,thiagosil/stringer,nobuti/stringer,dandorman/stringer,jeroenj/stringer,milandobrota/stringer,wwwjfy/stringer,bkbabydp/stringer,swanson/stringer,adscott/stringer,mpraglowski/stringer,jqr/stringer,swanson/stringer,dandorman/stringer,dperson/stringer,jqr/stringer,geemus/stringer,jeroenj/stringer,bkbabydp/stringer,nibble/stringer,dandorman/stringer,Koronen/stringer,milligramme/stringer,adscott/stringer,adscott/stringer,nobuti/stringer,run-project/stringer,InPermutation/stringer,nibble/stringer,mpraglowski/stringer,geemus/stringer,thiagosil/stringer,nibble/stringer,nobuti/stringer,jqr/stringer,milandobrota/stringer,Koronen/stringer,thiagosil/stringer,dperson/stringer,geemus/stringer,geemus/stringer,milandobrota/stringer,jeroenj/stringer,InPermutation/stringer,dperson/stringer,Koronen/stringer,swanson/stringer