pcre2_match_data: allow pcre2_match_data_create_from_pattern() with a NULL as the first parameter

[carenas]

would allow something like:

re = pcre2_compile(...);
can_jit = !pcre2_jit_compile(re, PCRE2_JIT_TEST_ALLOC);
md = pcre2_match_data_create_from_pattern(re, ...);
if (re != NULL && md != NULL) do {
  /* do some work here, including matches and maybe even some on demand JIT compilation */
} while (!done_matching_or_replacing)
/* do some cleanup here, no need to check for NULL when calling the corresponding `_free()` functions */

which matches a similar construct that uses pcre2_match_data_create() instead.

[zherczeg]

LGTM

[NWilson]

I suppose I can see why someone may want to do this, and it never hurts to add a null-check to make the behaviour defined. OK!