Don't skip disconnected X11 outputs

This change lets me use HDMI-0 (with HDMI dummy plugged in) as a
Sunshine exclusive output when using the following do/undo commands:
* xrandr --output HDMI-0 --mode 1920x1080 --right-of DP-0
* xrandr --output HDMI-0 --off

Author: luk1337

src/platform/linux/x11grab.cpp

@@ -409,7 +409,7 @@ struct x11_attr_t : public display_t {
       int monitor = 0;
       for(int x = 0; x < output; ++x) {
         output_info_t out_info { x11::rr::GetOutputInfo(xdisplay.get(), screenr.get(), screenr->outputs[x]) };
-        if(out_info && out_info->connection == RR_Connected) {
+        if(out_info) {
           if(monitor++ == streamedMonitor) {
             result = std::move(out_info);
             break;