Fix sensitivity based connectivity calculation (#1341)

Signed-off-by: Geoffroy Jamgotchian <geoffroy.jamgotchian@rte-france.com>

Author: geofjamg

src/main/java/com/powsybl/openloadflow/dc/fastdc/ConnectivityBreakAnalysis.java

@@ -180,7 +180,7 @@ private static boolean isGroupOfElementsBreakingConnectivity(LfNetwork lfNetwork
             for (ComputedElement element2 : computedElements) {
                 LfBranch branch = lfNetwork.getBranchById(element2.getLfBranch().getId());
                 ClosedBranchSide1DcFlowEquationTerm p = equationSystem.getEquationTerm(ElementType.BRANCH, branch.getNum(), ClosedBranchSide1DcFlowEquationTerm.class);
-                DenseMatrix elementMatrix = element2 instanceof ComputedContingencyElement ? contingenciesStates : actionStates;
+                DenseMatrix elementMatrix = element instanceof ComputedContingencyElement ? contingenciesStates : actionStates;
                 double value = Math.abs(p.calculateSensi(elementMatrix, element.getComputedElementIndex()));
                 sum += value;
             }