remove unused code

Author: vincentfretin

src/lib/entity.js

@@ -520,10 +520,6 @@ export function getComponentClipboardRepresentation(entity, componentName) {
   return `${componentName}="${attributes}"`;
 }
 
-function isEmpty(string) {
-  return string === null || string === '';
-}
-
 /**
  * Entity representation.
  */