fix Referencable.get_type crash when no solution given and 'is IN(ET1, ET2..) is used. Closes #81865

668:b2e231cbd9da introduces unrelated changes that 1. break tests, 2. make rql>0.30.1 incompatible with cw < 3.13.10

closes #74727: allow entity types to end with a capitalized letter provided they contain a lower-cased letter

containing HAVING comparison nodes where it's used and optional (eg outer join)

* & (bitwise AND),
* | (bitwise OR),
* # (bitwise XOR),
* << (bitwise left shift),
* >> (bitwise right shift)
* % (modulo),
* ^ (power),

allow optional on final relation (rhs only) and in having expression (hence Comparison node gain a 'optional' attribute). Closes #71415