Bug 299272 Renderer cannot handle an MPart with a null label
java.lang.IllegalArgumentException: Argument cannot be null at org.eclipse.swt.SWT.error(SWT.java:4049) at org.eclipse.swt.SWT.error(SWT.java:3983) at org.eclipse.swt.SWT.error(SWT.java:3954) at org.eclipse.e4.ui.widgets.CTabItem.setText(CTabItem.java:1013) at org.eclipse.e4.workbench.ui.renderers.swt.StackRenderer.showChild(StackRenderer.java:296) at org.eclipse.e4.workbench.ui.renderers.swt.LazyStackRenderer.processContents(LazyStackRenderer.java:92) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine.createGui(PartRenderingEngine.java:300) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine.createGui(PartRenderingEngine.java:349) at org.eclipse.e4.workbench.ui.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:54) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine.createGui(PartRenderingEngine.java:300) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine.createGui(PartRenderingEngine.java:349) at org.eclipse.e4.workbench.ui.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:54) at org.eclipse.e4.workbench.ui.renderers.swt.WBWRenderer.processContents(WBWRenderer.java:369) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine.createGui(PartRenderingEngine.java:300) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine.createGui(PartRenderingEngine.java:349) at org.eclipse.e4.ui.workbench.swt.internal.PartRenderingEngine$4.run(PartRenderingEngine.java:510)
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/workbench/ui/renderers/swt/StackRenderer.java
private int calcIndexFor(MElementContainer<MUIElement> stack,
			final MUIElement part) {
		int index = 0;
		
		for (MUIElement mPart : stack.getChildren()) {
			if (mPart == part)
				return index;
			if (mPart.isToBeRendered())
				index++;
		}
		return index;
	}
	@Override
	public void childRendered(
			final MElementContainer<MUIElement> parentElement,
			MUIElement element) {
		super.childRendered(parentElement, element);
		if (!(((MUIElement) parentElement) instanceof MPartStack)
				|| !(element instanceof MPart))
			return;
		showChild(parentElement, element);
		
		
		Control ctrl = (Control) element.getWidget();
		if (ctrl != null) {
			showTab(parentElement, element);
			stylingEngine.style(ctrl);
		}
	}
	private CTabItem findItemForPart(MElementContainer<MUIElement> stack,