Change a condition in emitHandleMemOp

[sandreenko]

if ((memBase != nullptr) && memBase->isContained() && (memBase->OperGet() == GT_CLS_VAR_ADDR))
should assert memBase->isContained() instead of checking it.

[sandreenko]

Also, change assert((amBaseReg != REG_NA) || (amIndxReg != REG_NA) || (indir->Offset() != 0)); // At least one should be set. to assert((amBaseReg != REG_NA) || (amIndxReg != REG_NA)); // At least one should be set. after that.