screen_refresh(): Fake a screen when the last one is removed (#2223)

Thanks to @ewhac for the suggestion.

Fixes: https://github.com/awesomeWM/awesome/issues/2221
Signed-off-by: Uli Schlachter <psychon@znc.in>

objects/screen.c

@@ -661,6 +661,10 @@ screen_refresh(void)
 
     screen_deduplicate(L, &new_screens);
 
+    /* Running without any screens at all is no fun. */
+    if (new_screens.len == 0)
+        screen_scan_x11(L, &new_screens);
+
     /* Add new screens */
     foreach(new_screen, new_screens) {
         bool found = false;
@@ -1176,6 +1180,11 @@ luaA_screen_fake_remove(lua_State *L)
         /* WTF? */
         return 0;
 
+    if (globalconf.screens.len == 1) {
+        luaA_warn(L, "Removing last screen through fake_remove(). "
+                "This is a very, very, very bad idea!");
+    }
+
     screen_array_take(&globalconf.screens, idx);
     luaA_object_push(L, s);
     screen_removed(L, -1);