Clone generatedUtilities before inserting

Author: adamwathan

src/lib/substituteTailwindAtRules.js

@@ -27,8 +27,13 @@ export default function(config, { components: pluginComponents }, generatedUtili
       }
 
       if (atRule.params === 'utilities') {
-        generatedUtilities.walk(node => (node.source = atRule.source))
-        atRule.before(generatedUtilities)
+        // This needs to be cloned here or utilities end up being empty
+        // in real projects. No idea why, struggling to reproduce in a
+        // test. Hot fixing to publish a patch.
+        const clonedUtilities = generatedUtilities.clone()
+
+        clonedUtilities.walk(node => (node.source = atRule.source))
+        atRule.before(clonedUtilities)
         atRule.remove()
       }
     })