2.4.5 causes an infinite loop in maildir_is_internal_name

Dear developers,

afte upgrading to the 2.4.5, all the imap-login processes always fall into infinite loops in maildir_is_inernal_name().

This is becuase, when mailbox_list_layout = fs, mlist->module_ctx.super.is_internal_name becomes the jus maidir_is_internal_name() itself, which causes infinite self-recursion loops (by a tail recursion optimization) as was the attached debug info shows.