SmartClient 6.5 - Support for explicitly null filter criteria values

[Isomorphic]

In SmartClient version 6.5, DataSources do not truly support having filter criteria with fields set explicitly to null. Omitting such fields from the filter criteria does work but either approach should be supported.
This patch avoids a Script error that can occur in some cases where DataBound components have explicitly null filter criteria field values.

//----------------------------------------------------------------------------
// Isomorphic SmartClient 6.5 patch
// Purpose: Handle explicit null criteria values. 
// 
// Applies to SmartClient 6.5 builds only
//----------------------------------------------------------------------------
if (window.isc && isc.version.startsWith("6.5/")) {
if (isc.DataSource) {
    isc.DataSource.addProperties({
        _fieldMatchesFilter:isc.DataSource.getPrototype().fieldMatchesFilter,
        fieldMatchesFilter:function (fieldValue, filterValue, requestProperties) {
            if (fieldValue == null) fieldValue = "";
            if (filterValue == null) filterValue = "";
            return this._fieldMatchesFilter(fieldValue, filterValue, requestProperties);
        }
    })
}

} else if (window.isc) {
  isc.Log.logWarn("Patch for SmartClient 6.5 builds included in this application. " +
            "You are currently running SmartClient verion '"+ isc.version + 
            "'. This patch is not compatible with this build and will have no effect. " +
            "It should be removed from your application source.");

}