fix sub apollo cache merge errors

lib/apollo.js

@@ -34,7 +34,12 @@ function getClient (uri) {
       freezeResults: true,
       typePolicies: {
         Sub: {
-          keyFields: ['name']
+          keyFields: ['name'],
+          fields: {
+            optional: {
+              merge: true
+            }
+          }
         },
         User: {
           // https://www.apollographql.com/docs/react/caching/cache-field-behavior/#merging-non-normalized-objects