Violated NoGood after backtracking

[rtaupe]

On commit 7855224 (current state of phase_saving_and_restarts), the following exception can occur:

Exception in thread "main" java.lang.RuntimeException: Violated NoGood after backtracking.! Should not happen.
        at at.ac.tuwien.kr.alpha.Util.oops(Util.java:101)
        at at.ac.tuwien.kr.alpha.solver.DefaultSolver.addAndBackjumpIfNecessary(DefaultSolver.java:260)
        at at.ac.tuwien.kr.alpha.solver.DefaultSolver.learnBackjumpAddFromConflict(DefaultSolver.java:291)
        at at.ac.tuwien.kr.alpha.solver.DefaultSolver.tryAdvance(DefaultSolver.java:198)
        at at.ac.tuwien.kr.alpha.solver.AbstractSolver$1.tryAdvance(AbstractSolver.java:34)
        at java.util.stream.ReferencePipeline.forEachWithCancel(Unknown Source)
        at java.util.stream.AbstractPipeline.copyIntoWithCancel(Unknown Source)
        at java.util.stream.AbstractPipeline.copyInto(Unknown Source)
        at java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
        at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(Unknown Source)
        at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(Unknown Source)
        at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
        at java.util.stream.ReferencePipeline.forEach(Unknown Source)
        at at.ac.tuwien.kr.alpha.Main.computeAndConsumeAnswerSets(Main.java:113)
        at at.ac.tuwien.kr.alpha.Main.main(Main.java:86)

It can be produced by invoking Alpha as follows:
alpha -i 0120-stable_marriage-n015.asp -i encoding-alpha.asp -n 10 --stats -gtc permissive -gtr strict -rs -b VSIDS_PHASE_SAVING -ph allfalse

Input files:
encoding-alpha.asp
0120-stable_marriage-n015.asp