Allure generate fails with NPE if test parameter value was null in allure 1 results

[smecsia]

If a parameter value was null in the results, produced by Allure version 1, allure generate throws an exception:

Exception in thread "main" java.lang.NullPointerException
	at io.qameta.allure.allure1.Allure1Plugin.lambda$getHistoryId$14(Allure1Plugin.java:406)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
	at java.util.stream.SortedOps$SizedRefSortingSink.end(SortedOps.java:352)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEachOrdered(ReferencePipeline.java:423)
	at io.qameta.allure.allure1.Allure1Plugin.getHistoryId(Allure1Plugin.java:404)
	at io.qameta.allure.allure1.Allure1Plugin.convert(Allure1Plugin.java:147)
	at io.qameta.allure.allure1.Allure1Plugin.lambda$null$1(Allure1Plugin.java:96)
	at java.util.ArrayList.forEach(ArrayList.java:1249)
	at io.qameta.allure.allure1.Allure1Plugin.lambda$readResults$2(Allure1Plugin.java:95)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(StreamSpliterators.java:312)
	at java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:742)
	at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
	at io.qameta.allure.allure1.Allure1Plugin.readResults(Allure1Plugin.java:94)
	at io.qameta.allure.ReportGenerator.lambda$readResults$0(ReportGenerator.java:27)
	at java.util.ArrayList.forEach(ArrayList.java:1249)
	at io.qameta.allure.ReportGenerator.readResults(ReportGenerator.java:27)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
	at io.qameta.allure.ReportGenerator.generate(ReportGenerator.java:48)
	at io.qameta.allure.ReportGenerator.generate(ReportGenerator.java:38)
	at io.qameta.allure.Commands.generate(Commands.java:64)
	at io.qameta.allure.CommandLine.run(CommandLine.java:129)
	at java.util.Optional.orElseGet(Optional.java:267)
	at io.qameta.allure.CommandLine.main(CommandLine.java:72)