Update HealthScript.lua

Bug fixed where red healthbar takes over half of your screen due so called "godmode".
(Due maxhealth being 0 or math.huge, both making width result in negative infinity)
With this fix whenever this happens, it'll just act as if on full health.
Merge pull request #4 from einsteinK/patch-1

[Bugfix] HealthScript - Healthbar filling almost whole screen