Comment 2 for bug 505732

In fact, instead of delete completely the information from the database, the missing plugin should say in the block he is missing. On the page we keep the block and if the plugin to display the artefact is missing the string "To display this content, the plugin "pluginname" is required, but is missing on this Mahara installation. Please contact your administrator to fix it".

And by the way, the Site Administration->Manage Plugins page should not stall if the plugin is missing from the disk.