fix: comparison of empty strings with like

[gramian]

What does this PR do?

This change fixes and tests the case of comparing two empty strings "" with LIKE, ie: SELECT ("" LIKE ""), see https://sqlfiddle.com/postgresql/online-compiler?id=357ca34a-0b9f-428d-8f17-10d3202e8a38 for comparison.

Related issues

https://github.com/ArcadeData/arcadedb/issues/1580

Additional Notes

The changed file contains a TODO, https://github.com/ArcadeData/arcadedb/blob/main/engine/src/main/java/com/arcadedb/query/sql/executor/QueryHelper.java#L35 which could be fixed to with this PR, but I haven't found a way yet to improve it.

Checklist

• [X] I have run the build using mvn clean package command
• [X] My unit tests cover both failure and success scenarios