fixing a type error

main/HSSF/Record/TextObjectRecord.cs

@@ -94,6 +94,9 @@ public TextObjectRecord(RecordInputStream in1)
                     throw new RecordFormatException("Read " + ptgs.Length
                             + " tokens but expected exactly 1");
                 }
+                if(!(ptgs[0] is OperandPtg)) {
+                    throw new ArgumentException("Had unexpected type of ptg at index 0: " + ptgs[0].GetType());
+                }
                 _linkRefPtg = (OperandPtg)ptgs[0];
                 if (in1.Remaining > 0)
                 {

testcases/ooxml/SS/Converter/TestExcelToHtmlConverterSuite.cs

@@ -14,15 +14,15 @@ public class TestExcelToHtmlConverterSuite
         private static List<String> failingFiles = new List<string>();
 
         [Test]
-        [Ignore("test")]
+
         public void TestExcelToHtmlConverter()
         {
             string[] fileNames = POIDataSamples.GetSpreadSheetInstance().GetFiles("*.xls");
             List<string> toConverter = new List<string>();
             StringBuilder stringBuilder = new StringBuilder();
             foreach (string filename in fileNames)
             {
-                if (filename.EndsWith(".xls"))
+                if (filename.EndsWith("clusterfuzz-testcase-minimized-POIHSSFFuzzer-6322470200934400.xls"))
                     toConverter.Add(filename);
                 else
                     continue;