Add a timeout: delay_exit_on_zero_displays

Outputs may disappear momentarily and come back later.
To prevent i3 from exit when no output is available momentarily, add a timeout delay_exit_on_zero_displays.

src/main.c

@@ -621,6 +621,8 @@ int main(int argc, char *argv[]) {
             ELOG("ERROR: No screen at (%d, %d), starting on the first screen\n",
                  pointerreply->root_x, pointerreply->root_y);
             output = get_first_output();
+            if (!output)
+                die("No usable outputs available.\n");
         }
 
         con_focus(con_descend_focused(output_get_content(output->con)));