The condition of an If requires a boolean value, true or false. You are giving it a string value.
What you want is to check if that string has a value and you do that with…
out_str_InVerification.IsNullOrEmpty
This will be true if it has no value, false if it has a value.
All that being said, you should do the free training on the UiPath web site. It teaches you these things.