fix(rewarded-ad): wrong signal when load ad failed

[kyoz]

This fix wrong signal fire when reward ad failed to load.

[gumaciel]

Thank you so much!

As I can see your change is correct, I will just test it in a few hours and approve if works.

[kyoz]

Yes, i just randomly figure it out when i use a toast to show "No video available" and without the fix, when turn the internet off and open the app. The toast just popup crazily. kk

[gumaciel]

Thank you, this should be fixed at #4 but was strangely unresolved