Fix build warnings in locale/programs/ld-ctype.c

This patch fixes the gcc warnings seen with gcc 9 -march>=z13 on s390x:
programs/ld-ctype.c: In function ‘ctype_read’:
programs/ld-ctype.c:1392:13: error: ‘wch’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
 1392 |    uint32_t wch;
      |             ^~~
programs/ld-ctype.c:1401:7: error: ‘seq’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
 1401 |    if (seq != NULL && seq->nbytes == 1)
      |       ^
programs/ld-ctype.c:1391:20: note: ‘seq’ was declared here
 1391 |    struct charseq *seq;
      |                    ^~~

Both seq and wch are uninitialized if get_character fails.
Thus we are now returning with an error.

ChangeLog:

	* locale/programs/ld-ctype.c (charclass_symbolic_ellipsis):
	Return error if get_character fails.