Fixed handling non-Ghost errors in Sentry

no issue

- in the near future, non-Ghost Ignition type errors will be coming into
  Sentry
- because they don't have a statusCode, they'll be rejected
- we want to detect if they're non-Ghost and still deal with them

core/shared/sentry.js

@@ -1,5 +1,6 @@
 const config = require('./config');
 const sentryConfig = config.get('sentry');
+const errors = require('@tryghost/errors');
 
 const expressNoop = function (req, res, next) {
     next();
@@ -19,6 +20,12 @@ if (sentryConfig && !sentryConfig.disabled) {
         requestHandler: Sentry.Handlers.requestHandler(),
         errorHandler: Sentry.Handlers.errorHandler({
             shouldHandleError(error) {
+                // Sometimes non-Ghost issues will come into here but they won't
+                // have a statusCode so we should always handle them
+                if (!errors.utils.isIgnitionError(error)) {
+                    return true;
+                }
+
                 // Only handle 500 errors for now
                 // This is because the only other 5XX error should be 503, which are deliberate maintenance/boot errors
                 return (error.statusCode === 500);