Fix tests and clarify first character access

py/repl.c

@@ -189,7 +189,7 @@ size_t mp_repl_autocomplete(const char *str, size_t len, const mp_print_t *print
                     if (dest[0] != MP_OBJ_NULL) {
                         // special case; filter out words that begin with underscore
                         // unless there's already a partial match
-                        if (s_len == 0 && *d_str == '_') {
+                        if (s_len == 0 && d_str[0] == '_') {
                             continue;
                         }
                         if (match_str == NULL) {

tests/cmdline/repl_autocomplete.py

@@ -7,6 +7,6 @@ x = '123'
 i = str
 i.lowe	('ABC')
 x = 5
-x.	
+x.	
 x._	
 None.	

tests/cmdline/repl_autocomplete.py.exp

@@ -12,7 +12,8 @@ Use \.\+
 'abc'
 >>> x = 5
 >>> x.
-from_bytes      to_bytes
+from_bytes      to_bytes
+>>> x.
 >>> x.__class__
 <class 'int'>
 >>> None.