updated for version 7.3.1127
Problem:    No error for using empty \%[].
Solution:   Give error message.
diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index 189e413..ec5543c 100644
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -977,6 +977,9 @@
 						      reg_magic == MAGIC_ALL);
 			    EMIT(c);
 			}
+			if (n == 0)
+			    EMSG2_RET_FAIL(_(e_empty_sb),
+						      reg_magic == MAGIC_ALL);
 			EMIT(NFA_OPT_CHARS);
 			EMIT(n);
 			break;