qasim-gui: Locker pid testing was buggy. Fixed.

bin/qasim-gui.rb

@@ -224,14 +224,18 @@ module Qasim
 		rescue Errno::EEXIST => e
 			# test if the other process still exist
 			masterpid = File.read(lockfname).strip
+			begin
 				Process.kill(0, masterpid.to_i)
 				warn "error: Another instance of %s is already running." % APP_NAME
 				exit 1
 			rescue Errno::ESRCH => e
+				fd = IO::sysopen( lockfname,
+								 Fcntl::O_WRONLY | Fcntl::O_EXCL )
 				f = IO.open(fd)
 				f.syswrite( "#{Process.pid}\n" )
 				f.close
 				@app.exec
+			end
 		ensure
 			masterpid = File.read(lockfname).strip
 			if masterpid.to_i == Process.pid then