Tweak the graphtool for this situation.

Basically, if the feedback popover is opened with the reveal button in a
graphtool problem, and the reveal button is not clicked before the
popover closes, then the graphtool timeout that is waiting for the
graphtool container to be shown errors out because it calls the
graphtool initialization method and there is no longer a graph container
in the DOM.  So just return if the graph container is not found.

htdocs/js/GraphTool/graphtool.js

@@ -9,6 +9,7 @@ window.graphTool = (containerId, options) => {
 	const gt = {};
 
 	gt.graphContainer = document.getElementById(containerId);
+	if (!gt.graphContainer) return;
 	if (gt.graphContainer.offsetWidth === 0) {
 		setTimeout(() => window.graphTool(containerId, options), 100);
 		return;