Parfor optimizer fails checking for block-partitioned inputs

Caused by: java.lang.RuntimeException: java.lang.NullPointerException
        at org.apache.sysml.parser.ParForStatementBlock.determineAccessPattern(ParForStatementBlock.java:588)
        at org.apache.sysml.parser.ParForStatementBlock.rDeterminePartitioningCandidates(ParForStatementBlock.java:539)
        at org.apache.sysml.parser.ParForStatementBlock.rDeterminePartitioningCandidates(ParForStatementBlock.java:526)
        at org.apache.sysml.parser.ParForStatementBlock.determineDataPartitionFormat(ParForStatementBlock.java:398)
        at org.apache.sysml.runtime.controlprogram.parfor.opt.OptimizerRuleBased.rewriteSetDataPartitioner(OptimizerRuleBased.java:423)
        at org.apache.sysml.runtime.controlprogram.parfor.opt.OptimizerRuleBased.optimize(OptimizerRuleBased.java:236)
        at org.apache.sysml.runtime.controlprogram.parfor.opt.OptimizationWrapper.optimize(OptimizationWrapper.java:246)
        at org.apache.sysml.runtime.controlprogram.parfor.opt.OptimizationWrapper.optimize(OptimizationWrapper.java:118)
        at org.apache.sysml.runtime.controlprogram.ParForProgramBlock.execute(ParForProgramBlock.java:601)
        at org.apache.sysml.runtime.controlprogram.Program.execute(Program.java:118)
        ... 13 more
Caused by: java.lang.NullPointerException
        at org.apache.sysml.parser.ParForStatementBlock$LinearFunction.equalSlope(ParForStatementBlock.java:1959)
        at org.apache.sysml.parser.ParForStatementBlock.isAlignedBlocking(ParForStatementBlock.java:595)
        at org.apache.sysml.parser.ParForStatementBlock.determineAccessPattern(ParForStatementBlock.java:580)