display: constrain line numbers on softwrapped lines with sprawling tabs

Check the column number, not the character index, when suppressing the
line number on chunks other than the first, since the index can be zero
when in fact we're on a later chunk.

This fixes https://savannah.gnu.org/bugs/index.php?51790.

src/winio.c

@@ -2352,7 +2352,7 @@ void edit_draw(filestruct *fileptr, const char *converted,
     if (margin > 0) {
 	wattron(edit, interface_color_pair[LINE_NUMBER]);
 #ifndef NANO_TINY
-	if (ISSET(SOFTWRAP) && from_x != 0)
+	if (ISSET(SOFTWRAP) && from_col != 0)
 	    mvwprintw(edit, row, 0, "%*s", margin - 1, " ");
 	else
 #endif