Executing match-delete with anonymous variable does not work

[vmax]

Description

Deleting in a match with anonymous variable does not work AND does not throw an error

Environment

1. OS (where Grakn server runs): macOS Catalina
2. Grakn version (and platform): 1.6.0
3. Grakn client: client-java

Reproducible Steps

Steps to create the smallest reproducible scenario:

1. Define team entity with attribute name
2. Insert one instance of team with name abc
3. Try running (does not delete)

tx.execute(match(var().isa("team").has("name", "abc")).delete());

4. Try running (does delete):

tx.execute(match(var("x").isa("team").has("name", "abc")).delete("x"));

Expected Output

Concepts deleted OR error thrown

Actual Output

Concepts silently not getting deleted