Add another getResolvedUrl test case

Author: matz3

test/test-css-variables-collector-plugin.js

@@ -67,4 +67,14 @@ describe("CSSVariablesCollectorPlugin.getResolvedUrl", function() {
 			null
 		);
 	});
+	it("Error: should return null when libraryName is not given", function() {
+		assert.strictEqual(
+			CSSVariablesCollectorPlugin.getResolvedUrl({
+				rawUrl: "img/foo.png",
+				filename: "/resources/sap/ui/foo/themes/base/Foo.less",
+				libraryName: undefined
+			}),
+			null
+		);
+	});
 });