Fixed missing child declaration

src/models/RunnerOrganisation.ts

@@ -1,4 +1,4 @@
-import { Entity, Column, ManyToOne, OneToMany } from "typeorm";
+import { Entity, Column, ManyToOne, OneToMany, ChildEntity } from "typeorm";
 import { IsOptional, } from "class-validator";
 import { RunnerGroup } from "./RunnerGroup";
 import { Address } from "./Address";
@@ -7,7 +7,7 @@ import { RunnerTeam } from "./RunnerTeam";
 /**
  * Defines a runner organisation (business or school for example).
 */
-@Entity()
+@ChildEntity()
 export class RunnerOrganisation extends RunnerGroup {
 
   /**