fix(patchers): ignore unset baseURL in @nextcloud/router

[ShGKme]

☑️ Resolves

• Talk Desktop defines the default value for baseUrl in @nextcloud/router requests, it is it not explicitly set
• But if it's set as undefined or other falsy value, Nextcloud Talk keeps it as a set value
• It results in requesting without baseURL
• Solution: only set baseURL if it is not actually set with truthy value

Example of the problematic place:
https://github.com/nextcloud/spreed/blob/29af6dac6325af9bba16b4706bb09066b601165e/src/utils/signaling.js#L980-L981

[Antreesy]

And signaling is back working!