fix(cli): stop printing <nil> at the end of kamel describe output

[tadayosi]

Before:

$ kamel describe platform camel-k
Name:                camel-k
Namespace:           test
Labels:              app=camel-k
Creation Timestamp:  Tue, 01 Jun 2021 15:48:58 +0900
Phase:               Ready
Version:             1.5.0-SNAPSHOT
Base Image:          adoptopenjdk/openjdk11:slim
Runtime Version:     1.7.0
Local Repository:    /tmp/artifacts/m2
Publish Strategy:    Spectrum
<nil>

After:

$ ./kamel describe ip camel-k
Name:                camel-k
Namespace:           test
Labels:              app=camel-k
Creation Timestamp:  Tue, 01 Jun 2021 15:48:58 +0900
Phase:               Ready
Version:             1.5.0-SNAPSHOT
Base Image:          adoptopenjdk/openjdk11:slim
Runtime Version:     1.7.0
Local Repository:    /tmp/artifacts/m2
Publish Strategy:    Spectrum