QVariant treats null variants as equal to zero

At present, the following expression returns true:

QVariant(int(0)) == QVariant(QVariant::Int)

(The latter creates a "null" QVariant.)

If this behaviour is intentional, the QVariant autotest (qtbase/tests/auto/corelib/kernel/qvariant/tst_qvariant.cpp) should be changed to eliminate the QEXPECT_FAIL call in the operator_eq_eq() test function (e.g. by checking isNull() also).

If the above behaviour is not intentional, the QVariant implementation should be corrected, which would also result in the QEXPECT_FAIL call being eliminated from the test.

In either case, the documentation should be updated to clarify the expected behaviour of null QVariants.