Description of problem: Kn resources are not showing in Topology if triggers has KSVC and IMC as subscriber

Prerequisites (if any, like setup, operators/versions): Install Serverless Operator

Steps to Reproduce

1. Create a KSVC
2. Create a Channel implementation i.e In Memory Channel  IMC 
3. Create a broker
4. Create a PingSource and sink to broker created above
5. Create a trigger subscribing broker to IMC
6. Create a trigger subscribing broker to KSVC

Actual results: 

Kn resources are not showing in Topology for above scenario as in below screenshots

Expected results: 

Kn resources should show in Topology for above scenario

Reproducibility (Always/Intermittent/Only Once): Always

Build Details: 4.7.0-0.nightly-2020-12-09-093341

Additional info: NPE is thrown for above scenario can be seen in below screenshot