fix defined? expression

`defined? a && b` is evaluated as `defined?(a && b)` and the return value always `expression`.

Author: ko1

lib/debug/server_dap.rb

@@ -183,7 +183,7 @@ def process
           send_response req, breakpoints: filters
         when 'configurationDone'
           send_response req
-          if defined? @is_attach && @is_attach
+          if defined?(@is_attach) && @is_attach
             @q_msg << 'p'
             send_event 'stopped', reason: 'pause',
                                   threadId: 1,