Bug fix #2788

in 3d window, nkey panel, click in middle of number button & press ESC
moved the 3d cursor to that location. The button was passing on its
event to the window event queue, which shouldn't be.

source/blender/src/interface.c

@@ -1583,7 +1583,7 @@ static int ui_do_but_TEX(uiBut *but)
 	ui_draw_but(but);
 	
 	if(dev!=ESCKEY) return but->retval;
-	else return 0;
+	else return B_NOP;	// prevent event to be passed on
 }