Fix warnings

Author: galderz

substratevm/src/com.oracle.graal.pointsto/src/com/oracle/graal/pointsto/reports/CallTreeCypher.java

@@ -23,7 +23,6 @@
 import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicInteger;
-import java.util.regex.MatchResult;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
@@ -148,10 +147,10 @@ private static void walkNodes(MethodNode methodNode, Map<Integer, Set<BciEndEdge
                     }
                 }
             } else {
-                final int virtualNodeId = addVirtualNode(invoke, virtualNodes);
-                addVirtualMethodEdge(methodNode.id, invoke, virtualNodeId, virtualEdges);
+                final int nodeId = addVirtualNode(invoke, virtualNodes);
+                addVirtualMethodEdge(methodNode.id, invoke, nodeId, virtualEdges);
                 for (Node calleeNode : invoke.callees) {
-                    addOverridenByEdge(virtualNodeId, calleeNode, overridenByEdges, nonVirtualNodes);
+                    addOverridenByEdge(nodeId, calleeNode, overridenByEdges, nonVirtualNodes);
                     if (calleeNode instanceof MethodNode) {
                         walkNodes((MethodNode) calleeNode, directEdges, virtualEdges, overridenByEdges, virtualNodes, nonVirtualNodes);
                     }