Keep sourcing when there is an error

Hello,

I want to know if there is any way to avoid source() stopping when there is
an error.
Here is the content of my Main.R script:

source("~/R/source/Constructor1.R") ?# Object1 should be constructed
ifelse(exists("Object1"), ? ? ? ? ? ?# It's an S4 object
? ? ? print("Object1 exists"), ? ? ?# I can't avoid using 'validity'
? ? ? print("Object1 doesn't exist."))

source("~/R/source/Main.R") is stopped at the first line when the object
isn't valid, the three other lines aren't sourced.

Thank you in advance.
--
Ronan