fix: not check index exclusion path for `null` values

[mrnagydavid]

This PR fixes issue #1327 🦕

Summary

Considering the following 4 types of index exclusions:

1. excludeFromindexes: ['foo.*']
2. excludeFromindexes: ['foo.bar']
3. excludeFromindexes: ['foo[].*']
4. excludeFromindexes: ['foo[].bar']

Supplying { entity: { foo: null } } throws for 2 and 3, but not for 1 and 4.

save({ excludeFromIndexes: ['foo.bar'], entity: { sho: 1, foo: null })
// throws TypeError: Cannot read properties of undefined (reading 'properties')

save({ excludeFromIndexes: ['foo[].*'], entity: { sho: 1, foo: null })
// throws TypeError: Cannot read properties of undefined (reading 'values')

With the changes in this PR, the save calls will not throw in any of the 4 cases.