[master < T1119] Return NULL on map projection from a null value

[antepusic]

This PR addresses Issue #1118, which is about making map projections from NULL values. In that case, Memgraph should return a NULL value without raising any exceptions.

[master < Task] PR

• Check, and update documentation if necessary
• Provide the full content or a guide for the final git message

Fix map projection behavior in case of null projection variable

To keep docs changelog up to date, one more thing to do:

• Write a release note here, including added/changed clauses

We’ve fixed a bug with map projection. If you project from a variable that happens to be null, the map projection will have a null value instead of displaying an error.

• Tag someone from docs team in the comments

[antepusic]

@vpavicic Release note in the original comment