thread.c: ignore result of blocking_region_begin
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38565 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
thread.c: ignore result of blocking_region_begin
the result of blocking_region_begin(), since it always is true in
that case. suppress "uninitialized" warnings.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38565 b2dd03c8-39d4-4d8f-98ff-823fe69b080e