patch 8.2.4579: cannot use page-up and page-down in the cmdline popup menu

Problem:    Cannot use page-up and page-down in the command line completion
            popup menu.
Solution:   Check for to page-up and page-down keys. (Yegappan Lakshmanan,
            closes #9960)
diff --git a/src/spellsuggest.c b/src/spellsuggest.c
index 1e38966..73ea210 100644
--- a/src/spellsuggest.c
+++ b/src/spellsuggest.c
@@ -509,7 +509,7 @@
 	// make sure we don't include the NUL at the end of the line
 	line = ml_get_curline();
 	if (badlen > (int)STRLEN(line) - (int)curwin->w_cursor.col)
-	    badlen = STRLEN(line) - curwin->w_cursor.col;
+	    badlen = (int)STRLEN(line) - (int)curwin->w_cursor.col;
     }
     // Find the start of the badly spelled word.
     else if (spell_move_to(curwin, FORWARD, TRUE, TRUE, NULL) == 0