Bug 66425: Avoid NullPointerExceptions found via poi-fuzz

We try to avoid throwing NullPointerException, but it was possible
to trigger one here

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1912281 13f79535-47bb-0310-9956-ffa450edef68

poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFChartSheet.java

@@ -90,8 +90,9 @@ public class XSSFChartSheet extends XSSFSheet  {
         XmlOptions xmlOptions = new XmlOptions(DEFAULT_XML_OPTIONS);
         xmlOptions.setSaveSyntheticDocumentElement(
                 new QName(CTChartsheet.type.getName().getNamespaceURI(), "chartsheet"));
-        chartsheet.save(out, xmlOptions);
-
+        if (chartsheet != null) {
+            chartsheet.save(out, xmlOptions);
+        }
     }
 
     private static byte[] blankWorksheet(){

poi-ooxml/src/test/java/org/apache/poi/ss/tests/TestWorkbookFactory.java

@@ -351,4 +351,12 @@ public final class TestWorkbookFactory {
             return false;
         }
     }
+
+    @Test
+    void testEncryptionNullPointerException() throws IOException {
+        assertThrows(IllegalArgumentException.class,
+                () -> WorkbookFactory.create(POIDataSamples.getSpreadSheetInstance().
+                        openResourceAsStream(
+                                "crash-9bf3cd4bd6f50a8a9339d363c2c7af14b536865c.xlsx")));
+    }
 }

poi/src/main/java/org/apache/poi/poifs/crypt/CryptoFunctions.java

@@ -252,9 +252,15 @@ public final class CryptoFunctions {
             if (cipherAlgorithm == CipherAlgorithm.rc4) {
                 cipher = Cipher.getInstance(cipherAlgorithm.jceId);
             } else if (cipherAlgorithm.needsBouncyCastle) {
+                if (chain == null) {
+                    throw new IllegalArgumentException("Did not have a chain for cipher " + cipherAlgorithm);
+                }
                 registerBouncyCastle();
                 cipher = Cipher.getInstance(cipherAlgorithm.jceId + "/" + chain.jceId + "/" + padding, "BC");
             } else {
+                if (chain == null) {
+                    throw new IllegalArgumentException("Did not have a chain for cipher " + cipherAlgorithm);
+                }
                 cipher = Cipher.getInstance(cipherAlgorithm.jceId + "/" + chain.jceId + "/" + padding);
             }