Consider total number of aggregations not number of non-empty aggrega…

…tions (#107536)

Test are failing because we are computing incorrectly the doc count error for terms aggregation. 
The only difference with the previous versions is that we are considering the number of empty aggregations
instead of the total number of aggregations when computing this value. Making this
change it makes the test happy.

server/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/AbstractInternalTerms.java

@@ -221,6 +221,7 @@ public final AggregatorReducer termsAggregationReducer(AggregationReduceContext
     private class TermsAggregationReducer implements AggregatorReducer {
         private final List<List<B>> bucketsList;
         private final AggregationReduceContext reduceContext;
+        private final int size;
 
         private long sumDocCountError = 0;
         private final long[] otherDocCount = new long[] { 0 };
@@ -236,6 +237,7 @@ private class TermsAggregationReducer implements AggregatorReducer {
         private TermsAggregationReducer(AggregationReduceContext reduceContext, int size) {
             bucketsList = new ArrayList<>(size);
             this.reduceContext = reduceContext;
+            this.size = size;
         }
 
         @Override
@@ -326,7 +328,7 @@ public InternalAggregation get() {
             if (sumDocCountError == -1) {
                 docCountError = -1;
             } else {
-                docCountError = bucketsList.size() == 1 ? 0 : sumDocCountError;
+                docCountError = size == 1 ? 0 : sumDocCountError;
             }
             return create(name, result, reduceContext.isFinalReduce() ? getOrder() : thisReduceOrder, docCountError, otherDocCount[0]);
         }