Initialize ctTampered in test

Author: mattia-moffa

tests/api/test_mlkem.c

@@ -3970,6 +3970,7 @@ int test_wc_mlkem_decap_fo_reject(void)
     word32 ctLen = 0;
 
     XMEMSET(ct, 0, sizeof(ct));
+    XMEMSET(ctTampered, 0, sizeof(ctTampered));
     XMEMSET(ss, 0, sizeof(ss));
 
     key = (MlKemKey*)XMALLOC(sizeof(*key), NULL, DYNAMIC_TYPE_TMP_BUFFER);