Fix error when caching zero results

src/main.rs

@@ -57,6 +57,13 @@ pub async fn report(
 
 async fn cache_report(db: &DatabaseConnection, models: &Vec<ReportEntry>) -> Result<()> {
     let models = models.iter().flat_map(|entry| entry.as_models());
+    let models = models.collect::<Vec<_>>();
+    debug!("Caching report entries: {:?}", models);
+
+    // TODO: Why is this needed?
+    if models.is_empty() {
+        return Ok(());
+    }
 
     TimeEntry::insert_many(models)
         .on_conflict(ReportEntry::grafting_conflict_statement())