fix: bt update -openerTabId works again

[atondwal]

We need to parse a bt tab id like 'a.X.Y' or even just 'Y' from a string
into an int, otherwise we get the following type errors, respectively:

Uncaught (in promise) Error: Type error for parameter updateProperties (Error processing openerTabId: Expected integer instead of "a.1.31") for tabs.update.

Uncaught (in promise) Error: Type error for parameter updateProperties (Error processing openerTabId: Expected integer instead of "31") for tabs.update.