neo4j_ustring_value() returns null pointer for empty strings

[johannessen]

According to the documentation, neo4j_ustring_value() always returns a valid pointer for a string.

https://majensen.github.io/libneo4j-omni/neo4j-client-doxy.html#_CPPv419neo4j_ustring_value13neo4j_value_t

However, for zero-length strings, no memory is allocated for the ustring field upon deserialisation. As a consequence, neo4j_ustring_value() returns a null pointer.

libneo4j-omni/lib/src/deserialization.c

Lines 664 to 679 in 1151ada

	char *ustring = NULL;
	if (length > 0)
	{
	ustring = neo4j_mpool_alloc(pool, length);
	if (ustring == NULL)
	{
	return -1;
	}
	if (neo4j_ios_read_all(stream, ustring, length, NULL) < 0)
	{
	return -1;
	}
	}
	*value = neo4j_ustring(ustring, length);

[johannessen]

I was thinking maybe there should be a const char * const with the empty string. neo4j_ustring_value() could then simply return that pointer for a zero-length string. Checking the string length would have a slight overhead though.