PROTON-1442: Some bugs found by Cursor Review Agent

A potential null pointer access, and a memory leak on error condition

Author: astitcher

cpp/src/messaging_adapter.cpp

@@ -137,7 +137,7 @@ void handle_transaction_coordinator_outcome(messaging_handler& handler, tracker
           case transaction_context::State::DISCHARGING:
             // Don't throw error here, instead close link with error
             make_wrapper(transaction_context->coordinator).close(error_condition{"amqp:not-allowed", "Received transaction declared disposition in invalid state"});
-            transaction_context.release();
+            transaction_context.reset();
         }
     } else if (pn_disposition_type(disposition) == PN_ACCEPTED) {
         switch (state) {
@@ -159,7 +159,7 @@ void handle_transaction_coordinator_outcome(messaging_handler& handler, tracker
           case transaction_context::State::DECLARED:
             // TODO: Don't throw error here, instead detach link or close session?
             make_wrapper(transaction_context->coordinator).close(error_condition{"amqp:not-allowed", "Received transaction accepted disposition in invalid state"});
-            transaction_context.release();
+            transaction_context.reset();
         }
     } else if (auto rejected_disp = pn_rejected_disposition(disposition); rejected_disp) {
         switch (state) {
@@ -181,7 +181,7 @@ void handle_transaction_coordinator_outcome(messaging_handler& handler, tracker
           case transaction_context::State::DECLARED:
             // TODO: Don't throw error here, instead detach link or close session?
             make_wrapper(transaction_context->coordinator).close(error_condition{"amqp:not-allowed", "Received transaction rejected disposition in invalid state"});
-            transaction_context.release();
+            transaction_context.reset();
         }
     }
     // TODO: Don't ignore unexpected disposition here, instead detach link or close session?

cpp/src/session.cpp

@@ -183,7 +183,7 @@ proton::tracker transaction_send_ctrl(sender&& coordinator, const symbol& descri
 
 void transaction_discharge(const session& s, bool failed) {
     auto& transaction_context = get_transaction_context(s);
-    if (transaction_context->state != transaction_context::State::DECLARED)
+    if (transaction_is_empty(s) || transaction_context->state != transaction_context::State::DECLARED)
         throw proton::error("Only a declared txn can be discharged.");
     transaction_context->state = transaction_context::State::DISCHARGING;