patch 8.1.2284: compiler warning for unused variable

Problem:    Compiler warning for unused variable. (Tony Mechelynck)
Solution:   Add #ifdef.
diff --git a/src/move.c b/src/move.c
index 484b931..d340f02 100644
--- a/src/move.c
+++ b/src/move.c
@@ -988,7 +988,9 @@
 	/* long line wrapping, adjust curwin->w_wrow */
 	if (curwin->w_wcol >= curwin->w_width)
 	{
+#ifdef FEAT_LINEBREAK
 	    char_u *sbr;
+#endif
 
 	    /* this same formula is used in validate_cursor_col() */
 	    n = (curwin->w_wcol - curwin->w_width) / width + 1;