Insert file browser into responder chain

This is required to have the object respond to various action methods such as cut:, copy:, paste:, and delete: — ideally though the class would handle it by itself, as OFB responsibility is bleeding into the document controller (though long-term I think it makes sense to instead let the document controller implement the OFB action methods).

Frameworks/DocumentWindow/src/DocumentController.mm

@@ -1204,6 +1204,12 @@ namespace
 			[self updateFileBrowserStatus:self];
 		}
 		self.layoutView.fileBrowserView = makeVisibleFlag ? self.fileBrowser.view : nil;
+
+		if(makeVisibleFlag)
+		{
+			self.fileBrowser.nextResponder = self.fileBrowser.view.nextResponder;
+			self.fileBrowser.view.nextResponder = self.fileBrowser;
+		}
 	}
 	[[self class] scheduleSessionBackup:self];
 }