Steps to reproduce:
1. Set a singe paragraph in content area - <p>some paragraph</p>
2. Select any part of it and apply FontName or RealFontSize command.

Workaround:
<telerik:RadEditor ID="RadEditor1" runat="server">
	<Content>
		<p>some paragraph</p>
	</Content>
</telerik:RadEditor>

<script type="text/javascript">
	(function () {
		var getValue = Telerik.Web.UI.Editor.InlineCommandWithValue.prototype.getValue;
		Telerik.Web.UI.Editor.InlineCommandWithValue.prototype.getValue = function (wnd, range) {
			try {
				if (!range || !this.settings.enableToolStateValue) return;
				if (!range.isCollapsed()) {
					range.normalizeEdges();
				}
				var startNode = range.startContainer;
				if (Telerik.Web.UI.Editor.Utils.isTextNode(startNode)) {
					startNode = startNode.parentNode;
				}
				else if (startNode.childNodes[range.startOffset] &&
					!Telerik.Web.UI.Editor.Utils.isTextNode(startNode.childNodes[range.startOffset])) {
					startNode = startNode.childNodes[range.startOffset];
				}
				return $telerik.getComputedStyle(startNode, this.settings.cssName) ||
					$telerik.getComputedStyle(startNode, this.getAltCssName(this.settings.cssName));
			} catch (e) {
				getValue.call(this, wnd, range);
			}
		}
	})();
</script>