Fix SIGFPE for vnc display of width/height = 1

During boot, the screen gets resized to height 1 and a mouse click at this
point will cause a division by zero when calculating the absolute pointer
position from the pixel (x, y). Return a click in the middle of the screen
instead in this case.
Signed-off-by: NChris Webb <chris@arachsys.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

vnc.c

@@ -1457,8 +1457,10 @@ static void pointer_event(VncState *vs, int button_mask, int x, int y)
         dz = 1;
 
     if (vs->absolute) {
-        kbd_mouse_event(x * 0x7FFF / (ds_get_width(vs->ds) - 1),
-                        y * 0x7FFF / (ds_get_height(vs->ds) - 1),
+        kbd_mouse_event(ds_get_width(vs->ds) > 1 ?
+                          x * 0x7FFF / (ds_get_width(vs->ds) - 1) : 0x4000,
+                        ds_get_height(vs->ds) > 1 ?
+                          y * 0x7FFF / (ds_get_height(vs->ds) - 1) : 0x4000,
                         dz, buttons);
     } else if (vnc_has_feature(vs, VNC_FEATURE_POINTER_TYPE_CHANGE)) {
         x -= 0x7FFF;