Bug fix: Fix --resize-damage

- Fix --resize-damage. I forgot to shrink the painting region back when
  actually copying to destination.

- Include extra pixels around the blur texture to avoid some possible
  small issues, if --resize-damage is positive.

- Known issue: Line artifacts may still appear with --dbe (X Render
  backend) or --glx-swap-method (GLX backend). I doubt if there's way to
  fix this without very inefficient mechanisms.

src/common.h

@@ -1599,6 +1599,9 @@ find_focused(session_t *ps) {
  */
 static inline XserverRegion
 copy_region(const session_t *ps, XserverRegion oldregion) {
+  if (!oldregion)
+    return None;
+
   XserverRegion region = XFixesCreateRegion(ps->dpy, NULL, 0);
 
   XFixesCopyRegion(ps->dpy, region, oldregion);