fix(trade): guard nil sortedResultTbl in dropdown tooltipFunc

The nil guard lost during the vaisest/trader-improvements merge
caused a crash when hovering the result dropdown after clearing
search results.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mcagnion

src/Classes/TradeQuery.lua

@@ -1009,8 +1009,15 @@ function TradeQueryClass:PriceItemRowDisplay(row_idx, top_pane_alignment_ref, ro
 		end
 	end
 	controls["resultDropdown"..row_idx].tooltipFunc = function(tooltip, dropdown_mode, dropdown_index, dropdown_display_string)
-		local pb_index = self.sortedResultTbl[row_idx][dropdown_index].index
-		local result = self.resultTbl[row_idx][pb_index]
+		local sortedRow = self.sortedResultTbl[row_idx]
+		if not sortedRow or not sortedRow[dropdown_index] then
+			return
+		end
+		local pb_index = sortedRow[dropdown_index].index
+		local result = self.resultTbl[row_idx] and self.resultTbl[row_idx][pb_index]
+		if not result then
+			return
+		end
 		local item = new("Item", result.item_string)
 		tooltip:Clear()
 		self.itemsTab:AddItemTooltip(tooltip, item, slotTbl)