FAPI: Fix segfault if Fapi_SetBranchCB is not called.

* An segfault did occur when PolicyOR is defined for an object but
  the callback for the branch selection was not set.
* The current auth object, when policy authorize nv was executed, was
  not set. So a strange string was passed to the callback as
  object path of the object to be authorized.

Signed-off-by: Juergen Repp <juergen_repp@web.de>

Author: JuergenReppSIT

src/tss2-fapi/ifapi_policy_callbacks.c

@@ -1533,9 +1533,11 @@ ifapi_exec_auth_nv_policy(
     if (fapi_ctx->policy.util_current_policy) {
         /* Use the current policy in the policy stack. */
         current_policy = fapi_ctx->policy.util_current_policy->pol_exec_ctx;
+        fapi_ctx->current_auth_object = fapi_ctx->policy.util_current_policy->pol_exec_ctx->auth_object;
     } else {
         /* Start with the bottom of the policy stack */
         current_policy = fapi_ctx->policy.policyutil_stack->pol_exec_ctx;
+        fapi_ctx->current_auth_object = fapi_ctx->policy.policyutil_stack->pol_exec_ctx->auth_object;
     }
     cb_ctx = current_policy->app_data;
     esys_ctx = fapi_ctx->esys;

src/tss2-fapi/ifapi_policyutil_execute.c

@@ -308,7 +308,9 @@ ifapi_policyutil_execute(FAPI_CONTEXT *context, ESYS_TR *session)
                     }
                     utl_ctx = utl_ctx->prev;
                 }
-                pol_util_ctx->pol_exec_ctx->session = ESYS_TR_NONE;
+                if (pol_util_ctx->pol_exec_ctx) {
+                    pol_util_ctx->pol_exec_ctx->session = ESYS_TR_NONE;
+                }
             }
             goto_if_error(r, "Execute policy.", error);