Don't show "Set template as default" snackbar if template creation failed

[SUPERCILEX]

This requires #274. With the current architecture, fixing a bug like this is basically impossible.

Here's where things fail:

Robot-Scouter/library/core-data/src/main/java/com/supercilex/robotscouter/core/data/model/Templates.kt

Lines 80 to 86 in 30438c9

	} catch (e: Exception) {
	ref.delete().logFailures("addTemplate:delete", ref)
	Dispatchers.Main { longToast(R.string.scout_add_template_not_cached_error) }
	logBreadcrumb("addTemplate:getDefaultTemplate: ${defaultRef.path}")
	throw InvocationMarker(e)
	}