Fix compressed PLY loading from older versions of SS.

[asundqui]

From this file: https://github.com/user-attachments/files/20961347/baltimore.ps.cleaned.compressed2.ply.zip
Looking at the PLY header we see this:

ply
format binary_little_endian 1.0
comment Generated by SuperSplat 1.8.3
element chunk 2626
property float min_x
property float min_y
property float min_z
property float max_x
property float max_y
property float max_z
property float min_scale_x
property float min_scale_y
property float min_scale_z
property float max_scale_x
property float max_scale_y
property float max_scale_z
element vertex 672077
property uint packed_position
property uint packed_rotation
property uint packed_scale
property uint packed_color
end_header

Interestingly for newer exports for SS compressed PLY the header looks like this:

ply
format binary_little_endian 1.0
comment Generated by SuperSplat 2.4.1
element chunk 31171
property float min_x
property float min_y
property float min_z
property float max_x
property float max_y
property float max_z
property float min_scale_x
property float min_scale_y
property float min_scale_z
property float max_scale_x
property float max_scale_y
property float max_scale_z
property float min_r
property float min_g
property float min_b
property float max_r
property float max_g
property float max_b
element vertex 7979586
property uint packed_position
property uint packed_rotation
property uint packed_scale
property uint packed_color

So newer exports from SS of compressed PLY also include min/max_r/g/b in their chunk properties, while older SS (possibly 1.* instead of 2.*?) don't include it. Looking through PlayCanvas sources it seems that if they aren't specified we simply assume min/max = 0/1 for those properties.

Loading it in Spark Editor vs. Super Splat appears to validate this approach. I'm able to load the above mentioned file in Spark without a problem now. This addresses the particular file loading issue in #72 .