Bug in export for -dIdentityPercent with no D hits

[PoslavskySV]

With -dIdentityPercents option and with no D hits:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at com.milaboratory.mixcr.export.FieldExtractors$28.extract(FieldExtractors.java:538)
at com.milaboratory.mixcr.export.FieldExtractors$28.extract(FieldExtractors.java:529)
at com.milaboratory.mixcr.export.FieldParameterless$1.extractValue(FieldParameterless.java:60)
at com.milaboratory.mixcr.export.InfoWriter.put(InfoWriter.java:82)
at com.milaboratory.mixcr.cli.ActionExportClones$ExportClones.run(ActionExportClones.java:151)
at com.milaboratory.mixcr.cli.ActionExportClones.go0(ActionExportClones.java:76)
at com.milaboratory.mixcr.cli.ActionExport.go(ActionExport.java:52)
at com.milaboratory.cli.JCommanderBasedMain.main(JCommanderBasedMain.java:155)
at com.milaboratory.mixcr.cli.Main.main(Main.java:123)