PolicyFromSpec: return nil on error

Returning nil wrapped in Policy interface along with error returns in an
interface with a nil value. This can't be used to perform a nil check.
To make it safe, turn nil value on error.

Signed-off-by: Sunny <darkowlzz@protonmail.com>

internal/policy/factory.go

@@ -38,5 +38,8 @@ func PolicerFromSpec(choice imagev1.ImagePolicyChoice) (Policer, error) {
 		return nil, fmt.Errorf("given ImagePolicyChoice object is invalid")
 	}
 
-	return p, err
+	if err != nil {
+		return nil, err
+	}
+	return p, nil
 }