Fixed a bug in list_to_binary

[fadushin]

malloc(0) returns NULL on ESP32, which results in an OUT_OF_MEMORY error. This PR checks handles the case where the size of the input list is 0 specially.

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

[pguyot]

Sorry. Does the problem occur on generic unix? If it only occurs on ESP32 we may want to have an ESP32 test instead.

[bettio]

Sorry. Does the problem occur on generic unix? If it only occurs on ESP32 we may want to have an ESP32 test instead.

glibc man page says:

NULL  may
also  be returned by a successful call to malloc() with a size of zero, or by a successful
call to calloc() with nmemb or size equal to zero.