Bug 48452 Widget is disposed while closing cool bar
This is the problem that is occurring in the nightly builds. There is something happening where a cool bar is attempting to layout disposed cool bar items.
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ToolBarContributionItem.java
toolBounds.x = point.x;
			toolBounds.y = point.y;
			
			if (chevronPosition.x >= toolBounds.x && chevronPosition.x - toolBounds.x <= toolBounds.width) {
				break;
			}
			visibleItemCount++;
		}
		
		if (chevronMenuManager != null) {
			chevronMenuManager.dispose();
		}
		chevronMenuManager = new MenuManager();
		for (int i = visibleItemCount; i < toolCount; i++) {
			IContributionItem data = (IContributionItem) tools[i].getData();
			if (data instanceof ActionContributionItem) {
				ActionContributionItem contribution = new ActionContributionItem(((ActionContributionItem) data).getAction());
				chevronMenuManager.add(contribution);
			} else if (data instanceof SubContributionItem) {
				IContributionItem innerData = ((SubContributionItem)data).getInnerItem();
				if (innerData instanceof ActionContributionItem) {
					ActionContributionItem contribution = new ActionContributionItem(((ActionContributionItem) innerData).getAction());
					chevronMenuManager.add(contribution);
				}
			} else if (data.isSeparator()) {
				chevronMenuManager.add(new Separator());
			}
		}
		Menu popup = chevronMenuManager.createContextMenu(coolBar);
		popup.setLocation(chevronPosition.x, chevronPosition.y);