HLS: check strtoull parsing

(cherry picked from commit a7984f0a1cd295f4b80a2003a30dda5ab3b315b0)
(cherry picked from commit cd84eec0f5d64bc4ea6289029cc737e0f8358296)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/stream_filter/httplive.c

@@ -541,15 +541,15 @@ static int string_to_IV(char *string_hexa, uint8_t iv[AES_BLOCK_SIZE])
     if (len <= 16) {
         iv_hi = 0;
         iv_lo = strtoull(string_hexa, &end, 16);
-        if (end)
+        if (*end)
             return VLC_EGENERIC;
     } else {
-        iv_lo = strtoull(&string_hexa[len-16], NULL, 16);
-        if (end)
+        iv_lo = strtoull(&string_hexa[len-16], &end, 16);
+        if (*end)
             return VLC_EGENERIC;
         string_hexa[len-16] = '\0';
-        iv_hi = strtoull(string_hexa, NULL, 16);
-        if (end)
+        iv_hi = strtoull(string_hexa, &end, 16);
+        if (*end)
             return VLC_EGENERIC;
     }