cov: Ignore fallback conditions

lib/core/middleware/error.js

@@ -88,6 +88,7 @@ async function readSource(frame) {
   }
 
   // Fallback: use server bundle
+  /* istanbul ignore if */
   if (!frame.contents) {
     frame.contents = this.resources.serverBundle.files[frame.fileName]
   }

lib/core/middleware/nuxt.js

@@ -42,6 +42,7 @@ module.exports = async function nuxtMiddleware(req, res, next) {
 
       preloadFiles.forEach(({ file, asType, fileWithoutQuery, extension }) => {
         // By default, we only preload scripts or css
+        /* istanbul ignore if */
         if (!shouldPush && asType !== 'script' && asType !== 'style') {
           return
         }