Fix/trade monitor freezing #4923 PR

Do you support submitting to the Pull Request process the following? Pull Request: The issue is due to various exchanges sporadically failing to fetch the last traded prices which causes the loop to fail entirely. The solution is simply to log the exception and continue looping. Addressing the individual exchanges' sporadic issues should happen in separate tasks. https://github.com/hummingbot/hummingbot/pull/4923