In the plugin, don't write properties if they're nil and also a number

[Dekkonot]

When sent through the network, NaN and Infinity become nil due to JSON not supporting them. This results in two problems:

• An annoying value of type nil cannot be converted to number warning in the output
• The value being reset to 0 instead of whatever value it was before

Neither of these are desirable, so this PR fixes that behavior. It does so by explicitly ignoring nil updates for Float32 and Float64 updates. This is explicitly on the 7.4.x branch because I don't want it to become permanent. Long-term, we want to swap to a different network protocol which should fix this issue.

See #953 for some discussion on this subject.