fix(tracker): guard VoiceOver questPlayButtons and AceGUI tree tooltip (#15)

Two crashes reported in #15 on Elune (1.6.3):

- TrackerUtils:IsVoiceOverLoaded only verified the VoiceOver addons were
  loaded, not that VoiceOver.QuestOverlayUI.questPlayButtons exists. Some
  VoiceOver builds expose a QuestOverlayUI without that table, so
  UpdateVoiceOverPlayButtons and SetAllPlayButtonAlpha crashed with
  'attempt to index field questPlayButtons (a nil value)'. Now verified in
  IsVoiceOverLoaded, which all play-button call sites gate on.

- AceGUIContainer-TreeGroup crashed indexing a nil AceGUI.tooltip when a
  conflicting addon registered a broken AceGUI-3.0 core (version 1.#INF)
  that won LibStub but never created the shared tooltip frame. The tree
  button handlers now lazily recreate it; widget version bumped 47->48 so
  the fixed widget wins registration.

Libs/AceGUI-3.0/widgets/AceGUIContainer-TreeGroup.lua

@@ -2,7 +2,10 @@
 TreeGroup Container
 Container that uses a tree control to switch between groups.
 -------------------------------------------------------------------------------]]
-local Type, Version = "TreeGroup", 47
+-- Version bumped 47 -> 48 (Questie-X): hardened Button_OnEnter/OnLeave against a nil
+-- AceGUI.tooltip caused by a conflicting addon's broken AceGUI-3.0 core. The bump ensures
+-- this fixed widget wins registration over an unpatched same-version copy.
+local Type, Version = "TreeGroup", 48
 local AceGUI = LibStub and LibStub("AceGUI-3.0", true)
 if not AceGUI or (AceGUI:GetWidgetVersion(Type) or 0) >= Version then return end
 
@@ -202,6 +205,13 @@ local function Button_OnEnter(frame)
 	self:Fire("OnButtonEnter", frame.uniquevalue, frame)
 
 	if self.enabletooltips then
+		-- AceGUI.tooltip can be nil when a conflicting addon registered a broken
+		-- AceGUI-3.0 core (seen in the wild as version "1.#INF") that won LibStub
+		-- but never created the shared tooltip frame. Lazily (re)create it so tree
+		-- button tooltips work instead of erroring with "attempt to index ... tooltip".
+		if not AceGUI.tooltip then
+			AceGUI.tooltip = CreateFrame("GameTooltip", "AceGUITooltip", UIParent, "GameTooltipTemplate")
+		end
 		local tooltip = AceGUI.tooltip
 		tooltip:SetOwner(frame, "ANCHOR_NONE")
 		tooltip:ClearAllPoints()
@@ -216,7 +226,7 @@ local function Button_OnLeave(frame)
 	local self = frame.obj
 	self:Fire("OnButtonLeave", frame.uniquevalue, frame)
 
-	if self.enabletooltips then
+	if self.enabletooltips and AceGUI.tooltip then
 		AceGUI.tooltip:Hide()
 	end
 end