The icons are not resolved by the REST API when no current theme is defined

java.lang.NullPointerException 
	at org.xwiki.icon.internal.DefaultIconManager.hasIcon(DefaultIconManager.java:142) 
	at org.xwiki.icon.internal.DefaultIconThemesResource.iconsByTheme(DefaultIconThemesResource.java:106) 
	at org.xwiki.icon.internal.DefaultIconThemesResource.getIcons(DefaultIconThemesResource.java:84) 
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
	at java.base/java.lang.reflect.Method.invoke(Method.java:566) 
	at org.restlet.ext.jaxrs.internal.wrappers.AbstractMethodWrapper.internalInvoke(AbstractMethodWrapper.java:162) 
	at org.restlet.ext.jaxrs.internal.wrappers.ResourceMethod.invoke(ResourceMethod.java:281) 
	at org.restlet.ext.jaxrs.JaxRsRestlet.invokeMethod(JaxRsRestlet.java:997) 
	at org.restlet.ext.jaxrs.JaxRsRestlet.handle(JaxRsRestlet.java:746)