Add TreeModel and HasSubtree implementation

src/orm/model/ModelResultIterable.ts

@@ -70,6 +70,11 @@ export class ModelResultIterable<T extends Model<T>> extends AbstractResultItera
      * @protected
      */
     protected async processEagerLoads(results: Collection<T>): Promise<void> {
+        if ( results.isEmpty() ) {
+            // Nothing to load relations for, so no reason to perform more queries
+            return
+        }
+
         const eagers = this.builder.getEagerLoadedRelations()
         const model = this.make<T>(this.ModelClass)
 
@@ -78,9 +83,10 @@ export class ModelResultIterable<T extends Model<T>> extends AbstractResultItera
 
             const relation = model.getRelation(name)
             const select = relation.buildEagerQuery(this.builder, results)
+            const resultCount = await select.get().count()
 
-            const allRelated = await select.get().collect()
-            allRelated.each(result => {
+            const allRelated = resultCount ? await select.get().collect() : collect()
+            results.each(result => {
                 const resultRelation = result.getRelation(name as any)
                 const resultRelated = resultRelation.matchResults(allRelated as any)
                 resultRelation.setValue(resultRelated as any)