Fix warnings about uninitialized instance variables

[ghost]

Fixes warning in formats/html.rb on line 243 about @css and warning in renderer/state.rb on line 83 about @names by first checking if the instance variable is defined.

[mfenner]

Will this be merged and released? Or what is the best way to suppress warning: instance variable @css not initialized with the current release?

[inukshuk]

You can change the verbosity of Ruby warnings, for example by setting RUBYOPT=W0 in your environment. This warning should also not be shown anymore in Ruby 3.0, but I'll address this and release the Gem so that the warning does not show on older Ruby versions either.

(The warning itself can be safely ignored in these cases; the instance variables are initialized to nil implicitly -- I guess that's why the warning is gone in Ruby 3.0)

[inukshuk]

Published 1.1.14 where these variables are initialized explicitly

[mfenner]

Thanks @inukshuk!