Builds for Haiku.

git-svn-id: https://www.unprompted.com/svn/projects/tildefriends/trunk@4584 ed5197a5-7fde-0310-b194-c3ffbd925b24

src/mem.c

@@ -436,6 +436,10 @@ void tf_free(void* ptr)
 
 char* tf_strdup(const char* string)
 {
+	if (!string)
+	{
+		return NULL;
+	}
 	size_t len = strlen(string);
 	char* buffer = tf_malloc(len + 1);
 	if ( buffer)