[fix][2p2c][test] Fix syntax for volvar deflection with global caching

dumux/porousmediumflow/2p2c/implicit/model.hh

@@ -172,10 +172,10 @@ public:
                     auto dofIdxGlobal = scv.dofIndex();
                     if (priVarSwitch_().wasSwitched(dofIdxGlobal))
                     {
-                        this->nonConstCurGlobalVolVars().volVars(dofIdxGlobal).update(this->curSol()[dofIdxGlobal],
-                                                                                      this->problem_(),
-                                                                                      element,
-                                                                                      scv);
+                        this->nonConstCurGlobalVolVars().volVars(scv.index()).update(this->curSol()[dofIdxGlobal],
+                                                                                     this->problem_(),
+                                                                                     element,
+                                                                                     scv);
                     }
                 }
             }