Fix 2 potential mod by 0 cases in ExpressionMod::evaluateInternal()

Issue 1
Division or modulo by zero results in undefined behavior.

Defect 98886 (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: 1996
Assigning: "rightInt" = "rhs.coerceToInt()". The value of "rightInt" is now 0.

            int rightInt = rhs.coerceToInt();

/src/mongo/db/pipeline/expression.cpp, line: 1997
In expression "left % rightInt", modulo by expression "rightInt" which may be zero has undefined behavior.

            return Value(left % rightInt);

Issue 2
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);