fix: only optimistically resolve nested entities (#298)

We have this optimization that nested entities will resolve id if it's
only requested field without making actual database query.

This might not be ideal, if relation is broken (for example Space references
not existing SpaceMetadata), but can save some queries, so it's mostly
just a convention.

However this ended up also short-circuting requests like this:
```gql
query {
  space(id: "eth:doesnotexist") {
    id
  }
}
```

This commit prevents this from happening, by checking if it was resolved
from parent.

src/graphql/resolvers.ts

@@ -194,29 +194,28 @@ export async function querySingle(
   const returnType = getNonNullType(info.returnType) as GraphQLObjectType;
   const jsonFields = getJsonFields(returnType);
 
-  const currentValue = parent?.[info.fieldName];
+  const parentResolvedValue = parent?.[info.fieldName];
 
-  if (currentValue === null) return null;
-  const alreadyResolvedInParent = typeof currentValue === 'object';
+  if (parentResolvedValue === null) return null;
+  const alreadyResolvedInParent = typeof parentResolvedValue === 'object';
   if (alreadyResolvedInParent) {
     return {
-      ...formatItem(currentValue, jsonFields),
+      ...formatItem(parentResolvedValue, jsonFields),
       _args: { block }
     };
   }
 
-  const id = currentValue || args.id;
-
   const parsed = parseResolveInfo(info);
-  if (parsed) {
+  if (parsed && parentResolvedValue) {
     // @ts-ignore
     const simplified = simplifyParsedResolveInfoFragmentWithType(parsed, returnType);
 
     if (Object.keys(simplified.fields).length === 1 && simplified.fields['id']) {
-      return { id, _args: { block } };
+      return { id: parentResolvedValue, _args: { block } };
     }
   }
 
+  const id = parentResolvedValue || args.id;
   const items = await context.getLoader(returnType.name.toLowerCase(), 'id', block).load(id);
   if (items.length === 0) {
     throw new Error(`Row not found: ${id}`);