Merlin
Using SDK VRCSDK3-UDON-2020.07.16.10.33_Public.unitypackage it is now not possible to set object reference fields to null in the inspector. This happens on both Udon Graph programs and Udon Sharp programs.
An easy repro is to put a public gameobject field on an Udon program and set it to reference some object in the scene. If you select the field and press delete the field will no longer get set to null whereas it did in the previous live Udon release.
This issue traces back to a small change that happened on line 186 of UdonProgramAsset.cs where a null check was added before setting variable values that prevents you from setting null to any public variable from the inspector. This null check should be removed.
Specifically this line:
if(!publicVariables.TrySetVariableValue(exportedSymbol, variableValue))
was changed to:
if(variableValue != null && !publicVariables.TrySetVariableValue(exportedSymbol, variableValue))
and should be reverted