add a condition to avoid FrozenError (#97)
add a condition to avoid FrozenError (#97)

* add a condition to avoid FrozenError

nil.to_s in Ruby 2.7.0 now always return a frozen String ""
a=nil.to_s
a.gsub!(//,'')
will raise a FrozenError (can't modify frozen String: "")

* `has_rdoc` is deprecated with no replacement

NOTE: Gem::Specification#has_rdoc= is deprecated with no replacement. It will be removed on or after 2018-12-01.
Gem::Specification#has_rdoc= called from ....../wikicloth/wikicloth.gemspec:19.
nricciar/wikicloth