WebLogic Portal: The requested URI null could not be found on this server

Weblogic Portal 10.3.2 throws this error for Struts 1.3 Porltet when “struts-adapter-1.3.jar” not on the classpath. The error vanishes once I got the jar on the classpath.

. 

The source of this error is:

com.bea.netuix.servlets.controls.content.ContentNotFoundException: The requested URI null could not be found on this server.
	at com.bea.netuix.servlets.controls.content.JspContent.beginRender(JspContent.java:584)
	at com.bea.netuix.nf.ControlLifecycle$7.visit(ControlLifecycle.java:485)
	at com.bea.netuix.nf.ControlTreeWalker.walkRecursiveRender(ControlTreeWalker.java:518)
	at com.bea.netuix.nf.ControlTreeWalker.walkRecursiveRender(ControlTreeWalker.java:529)
	at com.bea.netuix.nf.ControlTreeWalker.walkRecursiveRender(ControlTreeWalker.java:529)
	at com.bea.netuix.nf.ControlTreeWalker.walkRecursiveRender(ControlTreeWalker.java:529)
	at com.bea.netuix.nf.ControlTreeWalker.walk(ControlTreeWalker.java:220)
	at com.bea.netuix.nf.Lifecycle.processLifecycles(Lifecycle.java:399)
	at com.bea.netuix.nf.Lifecycle.processLifecycles(Lifecycle.java:361)
	at com.bea.netuix.nf.Lifecycle.processLifecycles(Lifecycle.java:352)
	at com.bea.netuix.nf.Lifecycle.run(Lifecycle.java:326)
	at com.bea.netuix.nf.UIControl.render(UIControl.java:582)