[IT-2819] Check in time if no data in backend available

Author: DanielSteger

src/main/groovy/de/iteratec/osm/result/dao/query/AggregationUtil.groovy

@@ -61,6 +61,9 @@ class AggregationUtil {
 
     static def getPercentile(List<Number> data, int percentage) {
         data = data.findAll {it != null}
+        if(data.size() == 0) {
+            return
+        }
         int index = (data.size() * (percentage.toFloat() / 100f)).toInteger()
         index = Math.min(data.size() - 1, Math.max(0, index))
         return getPercentileByIndex(data, index)