patch 8.2.4563: "z=" in Visual mode may go beyond the end of the line

Problem:    "z=" in Visual mode may go beyond the end of the line.
Solution:   Adjust "badlen".
diff --git a/src/spellsuggest.c b/src/spellsuggest.c
index ba3aaf3..3be917f 100644
--- a/src/spellsuggest.c
+++ b/src/spellsuggest.c
@@ -506,6 +506,10 @@
 	    curwin->w_cursor.col = VIsual.col;
 	++badlen;
 	end_visual_mode();
+	// make sure we don't include the NUL at the end of the line
+	line = ml_get_curline();
+	if (badlen > STRLEN(line) - curwin->w_cursor.col)
+	    badlen = STRLEN(line) - curwin->w_cursor.col;
     }
     // Find the start of the badly spelled word.
     else if (spell_move_to(curwin, FORWARD, TRUE, TRUE, NULL) == 0