Some times after enabling an app you’re not able to open the WebGUI of OwnCloud because of a white page / login loop due do a bug in this app.
Disabling via database access
The query to disable a specific app (in this example the storage_charts app) is this:
update oc_appconfig set configvalue="no" WHERE appid="storage_charts" AND configkey="enabled";
Disabling via occ command line script
Starting with ownCloud 6 the occ command line script is supporting disabling an app from a terminal. This is described in this tutorial:
Disabling by deleting the app folder
The third alternative is to just delete the folder of the app in: