handle empty url path

src/snapshot.ts

@@ -46,8 +46,11 @@ const URL_IN_CSS_REF = /url\((?:'([^']*)'|"([^"]*)"|([^)]*))\)/gm;
 const RELATIVE_PATH = /^(?!www\.|(?:http|ftp)s?:\/\/|[A-Za-z]:\\|\/\/).*/;
 const DATA_URI = /^(data:)([\w\/\+]+);(charset=[\w-]+|base64).*,(.*)/gi;
 export function absoluteToStylesheet(cssText: string, href: string): string {
-  return cssText.replace(URL_IN_CSS_REF, (_1, path1, path2, path3) => {
+  return cssText.replace(URL_IN_CSS_REF, (origin, path1, path2, path3) => {
     const filePath = path1 || path2 || path3;
+    if (!filePath) {
+      return origin;
+    }
     if (!RELATIVE_PATH.test(filePath)) {
       return `url('${filePath}')`;
     }

test/snapshot.test.ts

@@ -54,7 +54,7 @@ describe('absolute url to stylesheet', () => {
         href,
       ),
     ).to.equal(
-      `background-image: url('http://localhost/css/images/b.jpg');` +
+      `background-image: url('http://localhost/css/images/b.jpg'); ` +
         `background: #aabbcc url('http://localhost/css/images/a.jpg') 50% 50% repeat;`,
     );
   });
@@ -64,4 +64,8 @@ describe('absolute url to stylesheet', () => {
       absoluteToStylesheet('url(data:image/gif;base64,ABC)', href),
     ).to.equal('url(data:image/gif;base64,ABC)');
   });
+
+  it('can handle empty path', () => {
+    expect(absoluteToStylesheet(`url('')`, href)).to.equal(`url('')`);
+  });
 });