When downloading and running Bitcoin core for the first time, after clicking through the "Are you sure you want to open. it?" screen, there's a possibility that macOS will pass an argument like `-psn_0_SOME_ID` to the application, which results in a shutdown as it's an invalid argument:

![v0 19 0rc1 args shutdown](https://user-images.githubusercontent.com/863730/67034964-b026fc00-f0e6-11e9-8462-70d0fcf613e6.png)

This only happens on the first run, subsequent opens will work fine, but we should filter these out, otherwise it's a poor and confusing first experience.

{
    LOCK(csPathCached);
    fs::path &path = g_blocks_path_cache_net_specific;
    
    
    if (!path.empty()) return path;
    if (gArgs.IsArgSet("-blocksdir")) {
        path = fs::system_complete(gArgs.GetArg("-blocksdir", ""));
        if (!fs::is_directory(path)) {
            path = "";
            return path;
        }
    } else {
        path = GetDataDir(false);
    }
    path /= BaseParams().DataDir();
    path /= "blocks";
    fs::create_directories(path);
    return path;
}
const fs::path &GetDataDir(bool fNetSpecific)