[dev] [st] fix segfault

[anonymous]

This patch fixes segfault.  To reproduce, start selecting, move your
mouse out of window and back while holding LMB.

diff -r 6c311c25323e st.c
--- a/st.c      Wed Jun 08 21:35:58 2011 +0200
+++ b/st.c      Thu Jun 09 01:27:14 2011 +0400
@@ -615,7 +615,7 @@
                if(oldey != sel.ey || oldex != sel.ex) {
                        int starty = MIN(oldey, sel.ey);
                        int endy = MAX(oldey, sel.ey);
-                       drawregion(0, (starty > 0 ? starty : 0), term.col, 
(sel.ey < term.row ? endy+1 : term.row));
+                       drawregion(0, (starty > 0 ? starty : 0), term.col, 
(endy < term.row ? endy+1 : term.row));
                }
        }
 }