Bake reflection probes button no longer works and produces a nullref error

Unity: Lighting

6.0.X

6000.0.4f1 onwards

Reproduction:

Click Bake Reflection Probes in any APV project that has a reflection probe. For example HDRP sample template.

Result: Error and probes dont bake

Regression likely was introduced in this PR:

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This commit:

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