@@ -41,7 +41,7 @@ function replaceElement(element, options) {
     return;
   }
 
-  const elementClassAttr = element.getAttribute('class');
+  const elementClassAttr = element.getAttribute('class') || '';
   const classNames = (
     options.class ? `${options.class} ${elementClassAttr}` : elementClassAttr
   );
Original file line number	Diff line number	Diff line change
`@@ -41,7 +41,7 @@ function replaceElement(element, options) {`
`41`	`41`	`return;`
`42`	`42`	`}`
`43`	`43`
`44`		`- const elementClassAttr = element.getAttribute('class');`
	`44`	`+ const elementClassAttr = element.getAttribute('class') \|\| '';`
`45`	`45`	`const classNames = (`
`46`	`46`	options.class ? `${options.class} ${elementClassAttr}` : elementClassAttr
`47`	`47`	`);`