fix null-pointer occurring if Rodin tries to restore serialised disprover reasoner input

de.prob.eventb.disprover.core/src/de/prob/eventb/disprover/core/DisproverReasonerInput.java

 package de.prob.eventb.disprover.core;
 
-import org.eventb.core.seqprover.IProofTreeNode;
 import org.eventb.core.seqprover.IReasonerInput;
 import org.eventb.core.seqprover.proofBuilder.ReplayHints;
 
@@ -13,13 +12,6 @@ import org.eventb.core.seqprover.proofBuilder.ReplayHints;
  * @author jastram
  */
 public class DisproverReasonerInput implements IReasonerInput {
-
-	private final IProofTreeNode node;
-
-	public DisproverReasonerInput(IProofTreeNode node) {
-		this.node = node;
-	}
-
 	@Override
 	public void applyHints(ReplayHints renaming) {
 		// TODO Auto-generated method stub
@@ -37,7 +29,4 @@ public class DisproverReasonerInput implements IReasonerInput {
 		return false;
 	}
 
-	public IProofTreeNode getProofTreeNode() {
-		return node;
-	}
 }

de.prob.eventb.disprover.core/src/de/prob/eventb/disprover/core/internal/DisproverReasoner.java

@@ -70,7 +70,7 @@ public class DisproverReasoner implements IReasoner {
 			RodinDBException {
 
 		Set<Predicate> hypotheses = new HashSet<Predicate>();
-		for (Predicate predicate : sequent.visibleHypIterable()) {
+		for (Predicate predicate : sequent.hypIterable()) {
 			hypotheses.add(predicate);
 		}
 		Predicate goal = sequent.goal();
@@ -139,7 +139,7 @@ public class DisproverReasoner implements IReasoner {
 	@Override
 	public IReasonerInput deserializeInput(final IReasonerInputReader reader)
 			throws SerializeException {
-		return null;
+		return new DisproverReasonerInput();
 	}
 
 	@Override

de.prob.eventb.disprover.ui/src/de/prob/eventb/disprover/ui/DisproverTacticProvider.java

@@ -36,7 +36,7 @@ public class DisproverTacticProvider extends DefaultTacticProvider {
 		public ITactic getTactic(IProofTreeNode node, String globalInput,
 				String[] inputs) {
 
-			IReasonerInput reasonerInput = new DisproverReasonerInput(node);
+			IReasonerInput reasonerInput = new DisproverReasonerInput();
 			return BasicTactics.reasonerTac(
 					Disprover.createDisproverReasoner(), reasonerInput);
 		}