If we are being technical, you have more than 0.0000 health.
Minecraft health bar is terrible at accurately displaying health, with the amount of hearts you are seeing being possibly inaccurate, with a difference of up to 1 entire health point (in both directions, so your health could be almost a full health point lower or higher than the value you are being shown, for context: each full health point is supposed to be equal to half a heart, the maximum being 20 health).
What you are seeing here is a bug, which leads to a health value like 0.0021 being rounded down to 0 and being displayed as such by the health bar. Though I'd not be suprised if instead of a bug it turned out to be another instance of the health bar simply being stupid.