BUG : memory leak issue when storing field

Summary

With !499 (merged) the function object could be used multiple times but sometimes there is conflict when the field is stored in database.

Steps to reproduce

Use two instances of same FO e.g. heatTransferCoefficient without providing 'result' entry. It fails with error

--> FOAM FATAL ERROR: (openfoam-2112)
Failed to store pointer: heatTransferCoeff(T). Risk of memory leakage

Example case

Use tutorials/heatTransfer/buoyantPimpleFoam/hotRoom
Copy the FO in controlDict

    htc2
    {
        type            heatTransferCoeff;
        libs            (fieldFunctionObjects);
        field           T;
        writeControl    outputTime;
        writeInterval   1;
        htcModel        fixedReferenceTemperature;
        patches         (ceiling);
//        result          htc2;
        TRef            373;
    }

Running solver without 'result' entry will produce error

What is the current bug behaviour?

Attempts to 'store' field with same name

What is the expected correct behavior?

Probably more elegant error message or 'warning' with internal rename??

Environment information

OpenFOAM version : v2112

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