fix(UI): Potential fix for ElvUI/Plater combo

- Plater causes health bar to be loaded as Nameplate.unitFrame.healthBar, where ElvUI loads as Nameplate.unitFrame.Health, which was causing nil errors
- To avoid this, check for Nameplate.unitFrame.Health before using it to set icon size

HeroRotation/UI.lua

@@ -475,7 +475,7 @@
       local NameplateIconSize = Nameplate:GetHeight() / NameplateScaler;
       local HealthBar;
       if HR.GUISettings.General.NamePlateIconAnchor == "Life Bar" then
-        if _G.ElvUI and _G.ElvUI[1].charSettings.profile.nameplates.enable then
+        if _G.ElvUI and _G.ElvUI[1].charSettings.profile.nameplates.enable and Nameplate.unitFrame.Health then
           HealthBar = Nameplate.unitFrame.Health;
           NameplateIconSize = HealthBar:GetWidth() / 3.5;
         elseif _G.ShestakUI and _G.ShestakUI[2].nameplate.enable then