Don't throw error when petition plugin does not have DOM element
Don't throw error when petition plugin does not have DOM element

This was halting all script execution in IE11. Older templates won't
have the new petition dom element that's expected, so throwing an error
is incorrect behaviour.

SumOfUs/Champaign,SumOfUs/Champaign,SumOfUs/Champaign,SumOfUs/Champaign,SumOfUs/Champaign