patch 9.1.0701: crash with NFA regex engine when searching for composing chars

Problem:  crash with NFA regex engine when searching for composing chars
          (SuyueGuo)
Solution: When there is no composing character, break out of the loop
          and check that out1 state is not null

fixes: #15583

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index 6db4134..557d0e1 100644
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -6525,7 +6525,8 @@
 			else
 			    result = FAIL;
 
-			if (t->state->out->out1->c == NFA_END_COMPOSING)
+			if (t->state->out->out1 != NULL
+				&& t->state->out->out1->c == NFA_END_COMPOSING)
 			{
 			    end = t->state->out->out1;
 			    ADD_STATE_IF_MATCH(end);