fix(corelib): prevent duplicate child insertion in UIMiniWindowContainer (#1807)

Bug Fixes
- Improved mini-window placement when moving widgets between containers.
- Prevented widgets from remaining attached to an outdated parent during scheduled insertion.
- Preserved reliable insertion as target positions become available.

modules/corelib/ui/uiminiwindowcontainer.lua

@@ -176,21 +176,27 @@ function UIMiniWindowContainer:scheduleInsert(widget, index)
                 oldParent:removeChild(widget)
             end
             self:insertChild(index, widget)
+        end
 
-            while true do
-                local placed = false
-                for nIndex, nWidget in pairs(self.scheduledWidgets) do
-                    if nIndex - 1 <= self:getChildCount() then
+        while true do
+            local placed = false
+            for nIndex, nWidget in pairs(self.scheduledWidgets) do
+                if nIndex - 1 <= self:getChildCount() then
+                    local nOldParent = nWidget:getParent()
+                    if nOldParent ~= self then
+                        if nOldParent then
+                            nOldParent:removeChild(nWidget)
+                        end
                         self:insertChild(nIndex, nWidget)
-                        self.scheduledWidgets[nIndex] = nil
-                        placed = true
-                        break
                     end
-                end
-                if not placed then
+                    self.scheduledWidgets[nIndex] = nil
+                    placed = true
                     break
                 end
             end
+            if not placed then
+                break
+            end
         end
     end
 end