script: make scriptpubkey_is_p2tr available internally

For use by a later commit.

src/script.c

@@ -361,9 +361,10 @@ static bool scriptpubkey_is_p2wsh(const unsigned char *bytes, size_t bytes_len)
            bytes[1] == 32; /* SHA256 */
 }
 
-static bool scriptpubkey_is_p2tr(const unsigned char *bytes, size_t bytes_len)
+bool scriptpubkey_is_p2tr(const unsigned char *bytes, size_t bytes_len)
 {
-    return bytes_len == WALLY_SCRIPTPUBKEY_P2TR_LEN &&
+    /* Note this is called from elsewhere hence we check 'bytes' for NULL */
+    return bytes && bytes_len == WALLY_SCRIPTPUBKEY_P2TR_LEN &&
            bytes[0] == OP_1 && /* Segwit v1 */
            bytes[1] == 32; /* X-ONLY-PUBKEY */
 }

src/script.h

@@ -18,6 +18,8 @@ int script_get_push_opcode_size_from_bytes(
 /* Get OP_N */
 bool script_is_op_n(unsigned char op, bool allow_zero, size_t *n);
 
+bool scriptpubkey_is_p2tr(const unsigned char *bytes, size_t bytes_len);
+
 /* Convert 0-16 to OP_<N> */
 size_t value_to_op_n(uint64_t v);