Depending on the solution you’re looking for, you can use ifempty.
Instead of just filling in the mobile phone, you can add ifempty in front.
{{ifempty(1.Mobilephone; 12345678)}}
What this will do is if Mobilephone is empty, Make.com will fill in 12345678.
If you don’t want to fill in the contact if certain data is missing, adding a filter would be the best solution.
So ifempty replaces the value in case there’s nothing in there. This doesn’t change how the Google Contacts bit works, so if you instruct it to not fill in anything if there’s no phone number, you’re still getting that error. It just allows to you put in something else in case there’s no telephone number. That way your workflow can still function.
@Whoodini
The fields are required; we can’t leave them empty or use any other symbols because the value should be text or numerical. Therefore, we can do this.