is UPCA or EAN13. The old version returned an uninitialised Ref<Result>
(at the EAN13 case) which let MultiFormatUPCEANReader::decodeRow (line 90)
crash because a Result is assumed.
The bugfix is technically oriented at the java version.
Note: This error doesn't appear at normal tests because the MultiFormatUPCEANReader
uses the EAN13 reader for UPC-A detection. The UPCAReader is only used if
DecodeHints BarcodeFormat::UPC_A ist set.
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