[fix](statistics)Fix batch is null bug. (#36398)

This PR changed result sink logic:
#36053
Need to change the show column stats get row batch logic to avoid NPE.

fe/fe-core/src/main/java/org/apache/doris/qe/StmtExecutor.java

@@ -3346,9 +3346,14 @@ public List<ResultRow> executeInternalQuery() {
             try {
                 while (true) {
                     batch = coord.getNext();
-                    if (batch == null || batch.isEos()) {
+                    Preconditions.checkNotNull(batch, "Batch is Null.");
+                    if (batch.isEos()) {
                         return resultRows;
                     } else {
+                        // For null and not EOS batch, continue to get the next batch.
+                        if (batch.getBatch() == null) {
+                            continue;
+                        }
                         resultRows.addAll(convertResultBatchToResultRows(batch.getBatch()));
                     }
                 }