Verilog Translator

This exception appears when running ru.ispras.verilog.parser.sample.vis.VisFourByFourVerilogPrinterTestCase in the Retrascope MC Benchmark project.
The corresponding Verilog file:

retrascope-mc-benchmark/src/main/verilog/verilog2smv-vis-benchmarks/FourByFour/two.v

The error:

java.lang.NullPointerException
at ru.ispras.verilog.parser.processor.VerilogExprTransformer$4.apply(VerilogExprTransformer.java:278)
at ru.ispras.fortress.transformer.NodeTransformer.applyRule(NodeTransformer.java:166)
at ru.ispras.fortress.transformer.NodeTransformer.onOperationEnd(NodeTransformer.java:226)
at ru.ispras.fortress.expression.ExprTreeWalker.visitOperation(ExprTreeWalker.java:173)
at ru.ispras.fortress.expression.ExprTreeWalker.visitNode(ExprTreeWalker.java:123)
at ru.ispras.fortress.expression.ExprTreeWalker.visitOperation(ExprTreeWalker.java:160)
at ru.ispras.fortress.expression.ExprTreeWalker.visitNode(ExprTreeWalker.java:123)
at ru.ispras.fortress.expression.ExprTreeWalker.visit(ExprTreeWalker.java:93)
at ru.ispras.fortress.transformer.NodeTransformer.walk(NodeTransformer.java:54)
at ru.ispras.fortress.transformer.Transformer.transform(Transformer.java:230)
at ru.ispras.verilog.parser.processor.VerilogExprTransformer.transform(VerilogExprTransformer.java:62)
at ru.ispras.verilog.parser.elaborator.VerilogTransformer.transform(VerilogTransformer.java:159)
at ru.ispras.verilog.parser.elaborator.VerilogTransformer.transform(VerilogTransformer.java:170)
at ru.ispras.verilog.parser.elaborator.VerilogTransformer.transform(VerilogTransformer.java:189)
at ru.ispras.verilog.parser.elaborator.VerilogTransformer.onAssignStatementBegin(VerilogTransformer.java:78)
at ru.ispras.verilog.parser.walker.VerilogNodeVisitor$3.onBegin(VerilogNodeVisitor.java:265)
at ru.ispras.verilog.parser.walker.VerilogNodeVisitor.onBegin(VerilogNodeVisitor.java:700)
at ru.ispras.verilog.parser.core.TreeWalker.onBegin(TreeWalker.java:100)
at ru.ispras.verilog.parser.core.TreeWalker.start(TreeWalker.java:79)
at ru.ispras.verilog.parser.elaborator.VerilogTransformer.run(VerilogTransformer.java:53)
at ru.ispras.verilog.parser.elaborator.VerilogVariableSubstitutor.transform(VerilogVariableSubstitutor.java:44)
at ru.ispras.verilog.parser.elaborator.VerilogInstantiator.instantiateProcess(VerilogInstantiator.java:88)
at ru.ispras.verilog.parser.elaborator.VerilogDesign$1$1.next(VerilogDesign.java:185)
at ru.ispras.verilog.parser.elaborator.VerilogDesign$1$1.next(VerilogDesign.java:173)
at ru.ispras.verilog.parser.sample.VerilogDesignPrinter.start(VerilogDesignPrinter.java:36)
at ru.ispras.verilog.parser.VerilogDesignBackends.start(VerilogDesignBackends.java:56)
at ru.ispras.verilog.parser.VerilogTranslator.start(VerilogTranslator.java:169)
at ru.ispras.verilog.parser.sample.VerilogPrinter.main(VerilogPrinter.java:45)