Fix for unconverted once nodes

Gems/ScriptCanvas/Code/Include/ScriptCanvas/Grammar/AbstractCodeModel.cpp

@@ -3764,6 +3764,12 @@ namespace ScriptCanvas
                 nextSlot = onceResetSlot;
             }
 
+            if (!nextSlot)
+            {
+                AddError(ID.m_node->GetEntityId(), once, "Once node missing next slot, likely needs replacement");
+                return;
+            }
+
             ParseExecutionTreeBody(nextParse, *nextSlot);
             nextParse->MarkDebugEmptyStatement();
         }

Gems/ScriptCanvas/Code/Include/ScriptCanvas/Grammar/ParsingUtilities.cpp

@@ -928,6 +928,7 @@ namespace ScriptCanvas
         {
             return execution->GetId().m_node
                 && IsOnce(*execution->GetId().m_node)
+                && execution->GetId().m_slot
                 && execution->GetId().m_slot->GetType() == CombinedSlotType::ExecutionIn;
         }
 
@@ -938,7 +939,7 @@ namespace ScriptCanvas
 
         bool IsOnceReset(const Node& node, const Slot* slot)
         {
-            return slot = OnceProperty::GetResetSlot(&node);
+            return slot == OnceProperty::GetResetSlot(&node);
         }
 
         bool IsOperatorArithmetic(const ExecutionTreeConstPtr& execution)