tweaks: let update_line() return the correct value on error

If the given line is out of range of editwinrows, we don't display it
at all, so we obviously don't display more than one line of it.  Thus,
the return value in this case should be zero, not one.

src/winio.c

@@ -2683,8 +2683,9 @@ int update_line(filestruct *fileptr, size_t index)
 #endif
 	row = fileptr->lineno - openfile->edittop->lineno;
 
+    /* If the line is offscreen, don't even try to display it. */
     if (row < 0 || row >= editwinrows)
-	return 1;
+	return 0;
 
     /* First, blank out the row. */
     blank_row(edit, row, 0, COLS);