Fixed book not found when quantity did not exist

models/book.go

@@ -67,13 +67,11 @@ func GetBookByID(ID int64) (book Book, exists bool, err error) {
 	has, err := x.ID(ID).Get(&book)
 
 	if has {
-		// Get the books quantity. We can't join it because xorm ignores the Quantity option in struc
-		qt := Quantity{BookID: ID}
-		has, err = x.Desc("id").Get(&qt)
+		// Get the books quantity. We can't join it because xorm ignores the Quantity option in struct
+		book.Quantity, err = GetQuantityByBook(ID)
 		if err != nil {
 			fmt.Println("Error getting quantity:", err)
 		}
-		book.Quantity = qt.Quantity
 
 		// Get publisher. We can't join it because xorm ignores the PublisherID option in struct
 		publisher := Publisher{ID: book.Publisher}