You were correct in thinking it was the space that was the problem.
Unchecking all Target Dependencies is problematic. Target Dependencies is what tells the localization gathering processes not to gather text that’s already in those targets. If you localize everything that gets gathered for your game with no target dependencies specified, you’ll very likely end up localizing a bunch of stuff in your project that’s copied over from the engine or editor. You’ll spend unnecessary money and time on translations that your game doesn’t need, because we’ve already done them. I’ll investigate that this isn’t related to another path with a space being passed without quotation marks around it - it’s possible.
Indeed, you shouldn’t check Gather from Text Files if you have no source code. Alternatively, modifying the settings so that they don’t attempt to gather from the Source directory, which wouldn’t exist in a blueprint only project. I’ll make a note about warning the user, in this UI, if a specified directory doesn’t exist to gather from.
I’ve discovered the crash when no native culture is selected too. I’ll be fixing that momentarily and providing a changelist.