Catch if one page is broken https://github.com/sitespeedio/sitespeed.io/issues/4124 (#4495)

lib/plugins/html/renderer.js

@@ -30,6 +30,7 @@ export function renderTemplate(templateName, locals) {
     return getTemplate(templateName)(locals);
   } catch (error) {
     log.error('Could not generate %s, %s', templateName, error.message);
+    return `Could not generate ${templateName} error: ${error.message}`;
   }
 }
 export function addTemplate(templateName, templateString) {