Empty query string checks on server and driver are inconsistent

[james-whiteside]

The check for empty query strings that throws MISSING_QUERY on the driver side is weaker than the check on server side. This is the case for the Python driver and @farost says the Java driver too.

In the Python driver, the check is done by coercion of the string to a boolean, resulting in strings containing only whitespace to be considered non-empty:

typedb-driver/python/typedb/query/query_manager.py

Line 77 in 2df397c

if not query:

Meanwhile, the server considers the string empty and responds with the appropriate error.

This prevents the error from being caught before transmission to the server when it could be caught earlier.