google was nice to me and solved my own problem. for those of you having the same problem, you need to check some lines in your mimeapps.list:
i suggest to backup first. go to ~/.local/share/applications/, copy then rename pasted file of mimeapps.list to mimeapps.list.backup
open the original file, look for this line:
x-scheme-handler/trash=marlin.desktop
if your using nautilus, it must be trash=nautilus.desktop
make that line look like this (i'm using Pantheon File manager):
x-scheme-handler/trash=pantheon-trash.desktop
and pantheon-trash.desktop file must be on the same directory (~/.local/share/applications)
here's what pantheon-trash.desktop file looks like:
[Desktop Entry]
Name=Trash Folder
Comment=Open your personal trash folder
TryExec=pantheon-files
Exec=pantheon-files trash:///
Icon=trash
Terminal=false
StartupNotify=true
Type=Application
Categories=GNOME;GTK;Core;
OnlyShowIn=GNOME;Unity;
X-GNOME-Bugzilla-Bugzilla=GNOME
X-GNOME-Bugzilla-Product=pantheon-files
X-GNOME-Bugzilla-Component=general
X-Ubuntu-Gettext-Domain=pantheon-files
Name[en_PH]=pantheon-trash
here's my source: http://ubuntuforums.org/showthread.php?t=1861067