Issue Description: creating a custom perspective with maximum height in the negatives causes it to render as if its not set

• Dynmap Version: v3.3-beta-2
• Server Version: paper 1.18.1 build 77
• Pastebin of Configuration.txt: https://pastebin.com/700iVGMq
• Server Host (if applicable): self-hosted
• Other Relevant Data/Screenshots: https://github.com/webbukkit/dynmap/blob/v3.0/DynmapCore/src/main/java/org/dynmap/hdmap/IsoHDPerspective.java#L1237
• Steps to Replicate: create and use a custom perspective with maximumheight: -10 or any negative

[x] I have looked at all other issues and this is not a duplicate
[x] I have been able to replicate this

Should be fixed in 3.3-beta-3

Hi, I have the same issue

I have set-up two custom perspectives for diamond and copper mines

  - class: org.dynmap.hdmap.IsoHDPerspective
    name: iso_S_90_lowres_diamondmines
    azimuth: 180
    inclination: 90
    scale: 4
    minimumheight: -59
    maximumheight: -56
  - class: org.dynmap.hdmap.IsoHDPerspective
    name: iso_S_90_lowres_coppermines
    azimuth: 180
    inclination: 90
    scale: 4
    minimumheight: 46
    maximumheight: 49

The copper mines render just fine, the diamond mines render everything. The values for min/maxheight are ignored.

Copper mines:

Diamond mines: