[fix] if no background image, do not preload

frappe/templates/pages/desk.html

@@ -38,7 +38,9 @@
 	</div>
 
 	<!-- hack! load background image asap, before desktop is rendered -->
+	{% if background_image %}
 	<img src="{{ background_image }}" style="height: 1px; width: 1px; margin-bottom: -1px;">
+	{% endif %}
 
 	<script type="text/javascript" src="/assets/frappe/js/lib/jquery/jquery.min.js"></script>