Fix relation field unknown target object (#13129)

Fixes https://github.com/twentyhq/twenty/issues/12867

Issue:
when you have a variable `toto` which is: `Record<string, MyType>` and
you do toto['xxx'], this will be typed as `MyType` instead of `MyType |
undefined`

Solutions:
- activate `noUncheckedIndexedAccess` check in tsconfig, this is the
preferred solution but will take time to get there (this raises 600+
errors)
- use a Map: cf https://github.com/twentyhq/twenty/pull/13125/files
- set the type to Partial<Record<string, MyType>>. Drawback is that when
you do Object.values(toto), you'll get `Array<MyType | undefined>`.
Hence why we have to filter these behind


<img width="1512" alt="image"
src="https://github.com/user-attachments/assets/d0a0bfed-c441-4e53-84c2-2da98ccbcf50"
/>

packages/twenty-server/src/engine/api/graphql/workspace-query-runner/factories/query-result-getters/query-result-getters.factory.ts

@@ -19,9 +19,9 @@ import { PersonQueryResultGetterHandler } from 'src/engine/api/graphql/workspace
 import { WorkspaceMemberQueryResultGetterHandler } from 'src/engine/api/graphql/workspace-query-runner/factories/query-result-getters/handlers/workspace-member-query-result-getter.handler';
 import { CompositeInputTypeDefinitionFactory } from 'src/engine/api/graphql/workspace-schema-builder/factories/composite-input-type-definition.factory';
 import { FileService } from 'src/engine/core-modules/file/services/file.service';
+import { ObjectMetadataItemWithFieldMaps } from 'src/engine/metadata-modules/types/object-metadata-item-with-field-maps';
 import { ObjectMetadataMaps } from 'src/engine/metadata-modules/types/object-metadata-maps';
 import { isFieldMetadataInterfaceOfType } from 'src/engine/utils/is-field-metadata-of-type.util';
-import { ObjectMetadataItemWithFieldMaps } from 'src/engine/metadata-modules/types/object-metadata-item-with-field-maps';
 
 // TODO: find a way to prevent conflict between handlers executing logic on object relations
 // And this factory that is also executing logic on object relations
@@ -121,6 +121,10 @@ export class QueryResultGettersFactory {
   ): Promise<ObjectRecord> {
     const objectMetadataMapItem = objectMetadataMaps.byId[objectMetadataItemId];
 
+    if (!isDefined(objectMetadataMapItem)) {
+      throw new Error('Object metadata map item is not defined');
+    }
+
     const handler = this.getHandler(objectMetadataMapItem.nameSingular);
 
     const relationFields = Object.keys(record)