Fix crash if buyer out of funds

exchange.lua

@@ -1088,14 +1088,16 @@ function ex_methods.sell(self, p_name, ex_name, item_name, wear, amount, rate)
 			sql_error(db:errmsg())
 		end
 
-		local in_succ, in_err =
-			self:put_in_inbox(poster, item_name, wear, row_sold)
-		if not in_succ then
-			search_stmt:reset()
-			db:exec("ROLLBACK;")
-			return false, in_err
+		if not out_of_funds then
+			local in_succ, in_err =
+				self:put_in_inbox(poster, item_name, wear, row_sold)
+			if not in_succ then
+				search_stmt:reset()
+				db:exec("ROLLBACK;")
+				return false, in_err
+			end
 		end
-
+		
 		if poster ~= p_name then
 			local revenue = row_sold * row_rate