Revert "gui: use unsigned int to make gcc happy"

This reverts commit 9662a61a0eb09be0cdfcea4e2488aa16236b51fc.

We prefer 18babd44bcaee0c3eda3a7dceeb2cf685d92707e.
fix a compiler warning.
(cherry picked from commit 18babd44bcaee0c3eda3a7dceeb2cf685d92707e)