Null values in normalized GSP values

[zakwatts]

When hitting the GSP endpoints the expectedPowerGenerationNormalized values are returning null.

see images below to recreate issue.

This is somewhat similar to previous issue we had #333 for the national API endpoint.

Perhaps we can just exclude the normalised values, it would be good to establish what the use case is for it.

[yuvraajnarula]

hey @zakwatts
Can I work on this if it isn't flagged as internal for now? Will go through #333 for reference to plan things accordingly and get back to you,