修改量表计算接口计算结果为空的显示

graph-web/src/main/java/org/diagbot/graphWeb/work/ScaleCalculate.java

@@ -109,7 +109,7 @@ public class ScaleCalculate {
 
                 groupLists.add(groupResults);
             }
-            String text = null;
+            String text = "";
             Map<String, Object> calculate = (Map<String, Object>) data.get("calculate");
             List<Map<String, Object>> rangeList = (List<Map<String, Object>>) calculate.get("range");
             for (Map<String, Object> range : rangeList) {