get_main_branch() always running get_main_branch_config() even when it shouldn't

[D3SL]

Related to #767 , and how I found it. For some reason get_main_branch() is always running get_main_branch_config() even when it shouldn't because the tests on line 83 (remote %in% remote_list$name) and 85 (length(remote_main)) succeed.

There's 2 possibilities I can think of. The first is there's a build time issue leading to the tests failing in the function but working when the same lines of code are run interactively, or for some other reason the function isn't ending at the return() call and because the implied "else" clause isn't in an explicit else{} section get_main_branch_config() keeps getting run.

Parallel to all that length() is as in #767 not a good test for dataframes.