eqcompare: place the compare after the tooltip settles when Guda is loaded

Guda anchors its item tooltips with ANCHOR_NONE and its own SetPoint, and
the tooltip module then relocates every ANCHOR_NONE tooltip to its
configured spot. eqcompare picked left or right from GetLeft/GetRight
inside the Set* call -- against the position the tooltip was about to
leave -- so for an item in the left half of the screen the shopping
tooltips anchored to the right edge and rode the relocation off-screen
(vatichild/guda#41). Guda's own inventory block also widens the tooltip
after our hook has run.

With Guda present, resolve the link in the hook but hand the placement to
RunNextFrame, skipping it if the tooltip has hidden since. Guda lists
pfUI as a dependency, so it loads after us: gate on DoesAddOnExist and
flip the flag from ContinueOnAddOnLoaded. Without Guda the hook is
unchanged.

modules/eqcompare.lua

@@ -130,9 +130,28 @@ pfUI:RegisterModule("eqcompare", function ()
     SetTradeTargetItem = GetTradeTargetItemLink
   }
 
+  -- Guda anchors its item tooltips with ANCHOR_NONE and its own SetPoint, and
+  -- the tooltip module then moves every ANCHOR_NONE tooltip to its configured
+  -- spot. Reading the rect inside the Set* call picks the side against the
+  -- position the tooltip is about to leave, so place the compare a frame later.
+  local deferred
+  if C_AddOns.DoesAddOnExist("Guda") then
+    EventUtil.ContinueOnAddOnLoaded("Guda", function()
+      deferred = true
+    end)
+  end
+
   local function makeHook(getter)
     return function(tooltip, arg1, arg2, arg3)
-      ShowCompareItem(tooltip, getter(arg1, arg2, arg3))
+      local link = getter(arg1, arg2, arg3)
+      if not deferred then
+        return ShowCompareItem(tooltip, link)
+      end
+      RunNextFrame(function()
+        if tooltip:IsShown() then
+          ShowCompareItem(tooltip, link)
+        end
+      end)
     end
   end