RadiationSource behaves strangely at low intensity

[Alpaccalypse]

Description

If you have the RadiationSource component on an entity set to intensity: 0.1 they will never register on the geiger counter or cause any radiation poisoning. Changing slope to any value still results in no radiation. If you set intensity at 0.105, 0.11 etc, then it will behave as expected.

If you make a stack of 2 of this 0.1 intensity entity and place it in the environment or carry it, it will emit radiation, at approximately the correct values. Changing the slope value seems to cause minor variation from expected values when comparing the output of different stacks.

I have exhausted myself testing for now, but I think there is also a problem with something in the calculation mutliplying when it should be adding, or maybe some kind of compound error with the sum of the base values.

Reproduction

You can start testing it with something like this:

- type: entity
  parent: OreBase
  id: RadBase1
  suffix: rad ore test 11
  components:
  - type: Sprite
    state: uranium
  - type: Material
  - type: RadiationSource
    intensity: 0.11
    slope: 0.1

Screenshots
Intensity 0.11, slope 0.9, stack of two.

Intensity 0.1, slope 0.9, stack of two.

This might be expected, but it always seems to be off, even accounting for .01 and multiplication of values.

Additional context
I am so tired of testing this, and I might have either missed something obvious or made an obvious mistake somewhere, but I am certain that at least something is wrong here with it not registering 0.1 intensity correctly.

[Aeshus]

I suspect that this could be caused by RadiationMinIntensity (which defaults to 0.1).

space-station-14/Content.Shared/CCVar/CCVars.Radiation.cs

Lines 7 to 12 in e094b79

	/// <summary>
	/// What is the smallest radiation dose in rads that can be received by object.
	/// Extremely small values may impact performance.
	/// </summary>
	public static readonly CVarDef<float> RadiationMinIntensity =
	CVarDef.Create("radiation.min_intensity", 0.1f, CVar.SERVERONLY);

[Aeshus]

I think the CCVAR's comments are misleading at that's the not the minimum that can be received, but rather the maximum that will not be accepted.

space-station-14/Content.Server/Radiation/Systems/RadiationSystem.GridCast.cs

Lines 136 to 137 in e094b79

	if (rads <= MinIntensity)
	return null;