an icon in a menupopup is not well aligned horizontally

steps to reproduce

1. run the attached zul

result

When no specify iconSclas, the menuitem label is well aligned like the item no icon in the above picture.

workaround

	.z-menupopup [class^="z-icon"]{
		text-align: center;
		display:inline-block;
		min-width:16px;
		margin-right:9px;
	}