Heretic powerup visual effects conflict

In vanilla Heretic, using a shadowsphere together with powerups that affect the colormap of the player's view results in peculiar blending effects on the player's weapon sprite. This is most noticeable when using a Ring of Invincibility, where the environment correctly uses the golden invulnerability colormap in the translucency blend, but the weapon sprite is blended from its normal colors. It also manifests when using a torch in very dark areas, where the view will appear bright thanks to the torch, but the weapon appears as a dark shadow blended from the sector's natural light level.

Technical
This appears to be because R_DrawPSprite has an if/else chain for colormap selection that prioritizes the invisibility case over fullbright or fixed colormap, and assumes that the weapon should be lit normally when drawn with the shadowsphere in effect.