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Address code-gen issue 7 nil pointer when incorrect pkg name

**What this PR does / why we need it**:
When using the code-gen tool, if the comments in the ```doc.go``` file has a misspelled pkg name, it ends with a nil pointer. This can be difficult to debug. This PR fixes that by logging an error and continuing. 
https://github.com/kubernetes/code-generator/issues/7

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:
I was not sure whether just exiting here would be correct behaviour as reading the code , I noticed in other places it continues if the pkg is nil.
Also perhaps I should use the ```glog.V(5).info```  ?

```release-note
`NONE`
```