如何在R中对无效/错误位置的表进行地理编码？

I have collected data of different users' location from twitter. I am trying to plot those data in a map in R. The problem is users have given invalid/incorrect addresses which causes geocode function to fail. How can I avoid this failure? Is there any way to check for this error case and not proceed? For example the user location data is something like this for any file geocode9.csv. I have collected data of different users' locat