Avoid NPE in Job#getLastBuildsOverThreshold (#26005)

Co-authored-by: Tim Jacomb <[email protected]>

Author: mawinter69

core/src/main/java/hudson/model/Job.java

@@ -1053,6 +1053,9 @@ public RunT getLastCompletedBuild() {
      */
     public List<RunT> getLastBuildsOverThreshold(int numberOfBuilds, Result threshold) {
         RunT r = getLastBuild();
+        if (r == null) {
+            return Collections.emptyList();
+        }
         return r.getBuildsOverThreshold(numberOfBuilds, threshold);
     }