[bug-69021] add guard around cast

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1917779 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 8 insertions, 5 deletions

diff --git a/poi/src/main/java/org/apache/poi/hssf/model/InternalWorkbook.java b/poi/src/main/java/org/apache/poi/hssf/model/InternalWorkbook.java
index a60fec9fd6..a536d74dd0 100644
--- a/poi/src/main/java/org/apache/poi/hssf/model/InternalWorkbook.java
+++ b/poi/src/main/java/org/apache/poi/hssf/model/InternalWorkbook.java
@@ -1071,13 +1071,16 @@ public final class InternalWorkbook {
      *
      * Include in it ant code that modifies the workbook record stream and affects its size.
      */
-    public void preSerialize(){
+    public void preSerialize() {
         // Ensure we have enough tab IDs
         // Can be a few short if new sheets were added
-        if(records.getTabpos() > 0) {
-            TabIdRecord tir = ( TabIdRecord ) records.get(records.getTabpos());
-            if(tir.getTabIdSize() < boundsheets.size()) {
-                fixTabIdRecord();
+        if (records.getTabpos() > 0) {
+            Record rec = records.get(records.getTabpos());
+            if (rec instanceof TabIdRecord) {
+                TabIdRecord tir = ( TabIdRecord ) rec;
+                if(tir.getTabIdSize() < boundsheets.size()) {
+                    fixTabIdRecord();
+                }
             }
         }
     }