Fix ClassAttributeWithStaticValue handling of syntax errors

This linter would crash on hashes with syntax errors. Ignore this case
as the `RuboCop` linter will report syntax errors for us.

Change-Id: Idc23a378715656bb1978316f76c9e4ecbbdbbcdb
Reviewed-on: http://gerrit.causes.com/44343
Tested-by: jenkins <jenkins@brigade.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>