took into account breaking change in Java 21 - relates to github #1826

Author: dghgit

prov/src/main/java/org/bouncycastle/jce/provider/BouncyCastleProvider.java

@@ -276,7 +276,8 @@ public final Service getService(final String type, final String algorithm)
                         public Service run()
                         {
                             Service service = BouncyCastleProvider.super.getService(type, algorithm);
-                            if (service == null)
+                            // from Java21 services started to return with null class names...
+                            if (service == null || service.getClassName() == null)
                             {
                                 return null;
                             }

prov/src/test/java/org/bouncycastle/jce/provider/test/AlgorithmParametersTest.java

@@ -2,6 +2,7 @@
 
 import java.io.IOException;
 import java.security.AlgorithmParameters;
+import java.security.GeneralSecurityException;
 import java.security.Security;
 import java.security.spec.AlgorithmParameterSpec;
 import java.security.spec.DSAParameterSpec;
@@ -98,10 +99,25 @@ private void basicTest(String algorithm, Class algorithmParameterSpec, byte[] as
         }
     }
 
+    private void java21NullCheck()
+        throws Exception
+    {
+        try
+        {
+            AlgorithmParameters algParams = AlgorithmParameters.getInstance("1.2.840.113549.1.1.1", "BC");
+            fail("no exception");
+        }
+        catch (GeneralSecurityException e)
+        {
+            // okay..
+        }
+    }
+
     public void performTest()
         throws Exception
     {
         basicTest("DSA", DSAParameterSpec.class, dsaParams);
+        java21NullCheck();
 
         AlgorithmParameters al = AlgorithmParameters.getInstance("EC", "BC");