Fix free of garbage pointer. PR#3595

Reviewed-by: NEmilia Käsper <emilia@openssl.org>

crypto/ec/ec_mult.c

@@ -447,15 +447,16 @@ int ec_wNAF_mul(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
 	wNAF_len = OPENSSL_malloc(totalnum * sizeof wNAF_len[0]);
 	wNAF     = OPENSSL_malloc((totalnum + 1) * sizeof wNAF[0]); /* includes space for pivot */
 	val_sub  = OPENSSL_malloc(totalnum * sizeof val_sub[0]);
-		 
+
+	/* Ensure wNAF is initialised in case we end up going to err */
+	if (wNAF) wNAF[0] = NULL;	/* preliminary pivot */
+
 	if (!wsize || !wNAF_len || !wNAF || !val_sub)
 		{
 		ECerr(EC_F_EC_WNAF_MUL, ERR_R_MALLOC_FAILURE);
 		goto err;
 		}
 
-	wNAF[0] = NULL;	/* preliminary pivot */
-
 	/* num_val will be the total number of temporarily precomputed points */
 	num_val = 0;