fixed an assertion error

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@35390 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/queue/MappingWorksheet.java

@@ -109,7 +109,7 @@ public class MappingWorksheet {
         private ExecutorChunk(List<JobOffer> base, int index) {
             super(base);
             this.index = index;
-            assert base.size()>1;
+            assert !base.isEmpty();
             computer = base.get(0).executor.getOwner();
             node = computer.getNode();
         }
@@ -174,7 +174,7 @@ public class MappingWorksheet {
 
         private WorkChunk(List<SubTask> base, int index) {
             super(base);
-            assert base.size()>1;
+            assert !base.isEmpty();
             this.index = index;
             this.assignedLabel = base.get(0).getAssignedLabel();