NetBSD warnings

[XVilka]

../subprojects/sdb/src/query.c:756:20: warning: array subscript is of type 'char' [-Wchar-subscripts]
                                while (*val && isspace (*val)) {
                                               ^~~~~~~~~~~~~~
/usr/include/sys/ctype_inline.h:56:44: note: expanded from macro 'isspace'
#define isspace(c)      ((int)((_ctype_tab_ + 1)[(c)] & _CTYPE_S))
                                                ^~~~
../subprojects/sdb/src/query.c:760:22: warning: array subscript is of type 'char' [-Wchar-subscripts]
                                while (i >= 0 && isspace (cmd[i])) {
                                                 ^~~~~~~~~~~~~~~~
/usr/include/sys/ctype_inline.h:56:44: note: expanded from macro 'isspace'
#define isspace(c)      ((int)((_ctype_tab_ + 1)[(c)] & _CTYPE_S))
                                                ^~~~
2 warnings generated.