[singular][issue #2221] the plural builder method now nullchecks its argument with configurable results.

test/transform/resource/after-delombok/BuilderSingularToBuilderWithNullWithSetterPrefix.java

@@ -22,6 +22,7 @@ class BuilderSingularToBuilderWithNullWithSetterPrefix {
 		}
 		@java.lang.SuppressWarnings("all")
 		public BuilderSingularToBuilderWithNullWithSetterPrefix.BuilderSingularToBuilderWithNullWithSetterPrefixBuilder withElems(final java.util.Collection<? extends String> elems) {
+			if (elems == null) throw new java.lang.NullPointerException("elems cannot be null");
 			if (this.elems == null) this.elems = new java.util.ArrayList<String>();
 			this.elems.addAll(elems);
 			return this;