twa022 [1] filed a deletion request for xfce4-panel-vala0.48fix [2]:

The proper fix for compilation with vala 0.48 was merged upstream and included in the xfce4-panel 4.14.4 release that has been added to extra.

[1] https://aur.archlinux.org/account/twa022/ [2] https://aur.archlinux.org/pkgbase/xfce4-panel-vala0.48fix/