Uncaught Exception Error - Database Not Found

[alkatrivedi]

wrt PR - #2214

This is understood that if we are getting reference to cloud spanner database using const database = instance.database(databaseId); the database needs to be exists already

but if we are getting reference to database which doesn't exists, it is throwing an unhandled exception error

Error: 5 NOT_FOUND: Database not found

- Steps to reproduce

https://github.com/googleapis/nodejs-spanner/blob/main/samples/crud.js#L187-#L229

Run the sample queryData and pass the databaseId which doesn't exists

Running sample is triggering Uncaught Exception which needs to be handle properly