Division or modulo by zero results in undefined behavior.

Defect 98887 (STATIC_C)
Checker DIVIDE_BY_ZERO (subcategory none)
File: /src/mongo/db/pipeline/expression.cpp
Function mongo::ExpressionMod::evaluateInternal(mongo::Variables *) const
/src/mongo/db/pipeline/expression.cpp, line: 1990
Assigning: "rightLong" = "rhs.coerceToLong()". The value of "rightLong" is now 0.

                long long rightLong = rhs.coerceToLong();

/src/mongo/db/pipeline/expression.cpp, line: 1991
In expression "left % rightLong", modulo by expression "rightLong" which may be zero has undefined behavior.

                return Value(left % rightLong);