RESOLVED - BATCH-589: StepExecutionResourceProxy's toString() leads to NPE

added assertion delegate is not null in toString (similar to other methods) and removed the toString usage in FlatFileItemReader#setResource

spring-batch-core/src/main/java/org/springframework/batch/core/resource/StepExecutionResourceProxy.java

@@ -291,9 +291,9 @@ public class StepExecutionResourceProxy extends StepExecutionListenerSupport imp
 	 * Delegates to the proxied Resource.
 	 */
 	public String toString() {
+		Assert.state(delegate != null, "The delegate resource has not been initialised. "
+				+ "Remember to register this object as a StepListener.");
 		return delegate.toString();
 	}
-	
-	
 
 }