PHP Fatal error: Call to undefined function panels_panel_context_get_display() in

The panels_panel_context_get_display() is actually defined in plugins/task_handlers/panel_context.inc of the Panels module. In order to ensure that this file is available, the function page_manager_get_task_handler('panel_context'); is called beforehand. In order to protect against configuration inconsistencies like the one you experienced (panel_context.inc is not loadable but there are still panels defined with panel_context handler), we should check the return value of page_manager_get_task_handler and bail out early if necessary.

Uh, stupid me.

Committed and pushed: e3ea84d