Commit 9ec8eee23ecbbb0176996542d054758262500240 had removed the custom
actions prev_error & next_error in favour of some global actions with
global shortcut, which would dynamically decide which result tool view to
apply the action (e.g. by shortcut) on. Two things were forgotten:
a) the plugin still installed a ui.rc file for those actions
b) The OutputWidget still tried to get the two actions by their id from
the plugin, to insert it into its own UI. Later the commit
fc8d34f0b00a9d0f4bbf480b06a34a9190b46d20 also added generic actions to
the widget. As a result of the failing action fetching two warnings
QWidget::insertAction: Attempt to insert null action
were seen on the log.
This commit fixes both by removing the no longer useful code.