Fix switching out of full mode when started in connector mode
Fix switching out of full mode when started in connector mode

Previously, if Standalone was open and Firefox was opened in connector
mode, ZoteroOverlay.onLoad() was never run, which meant that, among
other things, the before-reload handler that closed the Zotero pane when
switching out of full mode was never added.

gracile-fr/zotero,gracile-fr/zotero,gracile-fr/zotero