[master < ] Fix segfault based on issue #874

[DavIvek]

This PR is about handling queries in which we want to set a property of a null label, for example, SET null.a = 1. This type of query would cause a segmentation fault and would crash the database. To prevent this, QueryRunTimeException will be thrown.

[master < Task] PR

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

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

• Write a release note here, including added/changed clauses
• Tag someone from docs team in the comments

@vpavicic

[gitbuda]

• the error string can be a bit more condensed/packed (smaller)
• in the error message user won't understand what an operator is (if it's not known from before), we should like this part of memgraph docs -> https://memgraph.com/docs/memgraph/reference-guide/inspecting-queries#operators (you should use the shortened link)

[Ignition]

It would be nice to have better insight into the root cause.
This is a problem with operator creation.
SetProperty can handle null values at execution, for example UNWIND [null] AS x SET x.a = 1 is fine. So what is it about construction of operators that has an issue with null literals for example SET null.a = 1?

[Josipmrden]

No comments from my side on the code except:

• branch name could be better (e.g. fix-crash-on-null-values-for-switch-case)
• Update the info for PR describing what is the fix about and on what query it works.

[DavIvek]

Even though throwing this exception isn't the solution to a problem with operator creation, it will prevent segmentation fault. We can leave issue #874 open and for mg-v2.12.0 find the root cause of the problem.