F-5633: use explicit NULL comparison in FreeCiphers

Use the project's preferred `ptr != NULL` form for the new DTLS 1.3 ChaCha
record-number zeroization guards instead of relying on truthiness.

Author: julek-wolfssl

src/internal.c

@@ -3343,9 +3343,9 @@ void FreeCiphers(WOLFSSL* ssl)
     ssl->dtlsRecordNumberDecrypt.aes = NULL;
 #endif /* BUILD_AES */
 #ifdef HAVE_CHACHA
-    if (ssl->dtlsRecordNumberEncrypt.chacha)
+    if (ssl->dtlsRecordNumberEncrypt.chacha != NULL)
         ForceZero(ssl->dtlsRecordNumberEncrypt.chacha, sizeof(ChaCha));
-    if (ssl->dtlsRecordNumberDecrypt.chacha)
+    if (ssl->dtlsRecordNumberDecrypt.chacha != NULL)
         ForceZero(ssl->dtlsRecordNumberDecrypt.chacha, sizeof(ChaCha));
     XFREE(ssl->dtlsRecordNumberEncrypt.chacha, ssl->heap, DYNAMIC_TYPE_CIPHER);
     XFREE(ssl->dtlsRecordNumberDecrypt.chacha, ssl->heap, DYNAMIC_TYPE_CIPHER);