Ruby » Ruby master

merge revision(s) 63417: [Backport #14756]

    error.c: check redefined backtrace result

    * error.c (rb_get_backtrace): check the result of `backtrace` even
      if the method is redefined.  [ruby-core:87013] [Bug #14756]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@64147 b2dd03c8-39d4-4d8f-98ff-823fe69b080e