[uforead] tx dump of CID-keyed UFO reports an extra empty FDict in the FDArray

[punchcutter]

You can see this using the test file tx tests/tx_data/input/cidkeyed-with-multiple-fdicts.ufo

## FontDict[0]
FontName            "FDArraySelect.0.Alphabetic"
## Private
BlueValues          {-18,0,521,538,746,764}
OtherBlues          {-283,-283,-273,-273}
StdHW               34
StdVW               55
StemSnapH           {34,59}
StemSnapV           {36,55,64}
## FontDict[1]
FontName            "FDArraySelect.1.AlphabeticDigits"
## Private
BlueValues          {-18,0,746,764}
StdHW               32
StdVW               55
StemSnapH           {32,48,108}
StemSnapV           {55,66,109}
## FontDict[2]
FontName            "FDArraySelect.5.Generic"
## Private
BlueValues          {-250,-250,1100,1100}
StdHW               40
StdVW               40
StemSnapH           {40,120}
StemSnapV           {40,120}
LanguageGroup       1
## FontDict[3]
## Private
BlueScale           0
BlueShift           0
BlueFuzz            0
StdHW               0
StdVW               0
ExpansionFactor     0

FontDict[3] doesn't actually exist so shouldn't be displayed.