Check for Ractor constant

TruffleRuby support

Author: tenderlove

lib/sqlite3/database.rb

@@ -183,7 +183,7 @@ def initialize file, options = {}, zvfs = nil
 
       initialize_extensions(options[:extensions])
 
-      ForkSafety.track(self) if Ractor.main == Ractor.current
+      ForkSafety.track(self) if !defined?(Ractor) || (Ractor.main == Ractor.current)
 
       if block_given?
         begin