Fixed some stuff not getting checked against null

ref #39 gosh i sometimes hate js types

src/models/actions/CreateGroupContact.ts

@@ -56,7 +56,7 @@ export class CreateGroupContact {
      * Get's this participant's address from this.address.
      */
     public async getAddress(): Promise<Address> {
-        if (this.address === undefined) {
+        if (this.address === undefined || this.address === null) {
             return null;
         }
         if (!isNaN(this.address)) {