vector_to_random_points: Change default value of geometry_count to null?

[m-mohr]

For full context see: #315 (comment)

In the end, @soxofaan wrote:

[...] I think there are two concerns I want to tackle simultaneously:

• giving geom_count=null and total_count=null currently causes CountsMissing error. I think we should provide a non-error behavior (e.g. 1 sample per geometry)
• if the user just want to specify total_count=100, they should not forget to also explicitly set geom_count to null otherwise it won't work and they just get 1 sample per geometry (because that is the default for geom_count). I don't like this UI/UX-wise.

My proposal to tackle both is:

• give geom_count default value null
• allow geom_count=null + total_count=null : 1 sample per geometry

Achieving the latter can be done (instead of the "dynamic" total_count default value trick I suggested earlier) by replacing the note about CountsMissing with something like:

If geometry_count and total_count are both unrestricted (i.e. set to null), one sample per geometry is used.