fix: Fix memory leak in EventQueue

Previously empty event targets were never fully removed from EventQueue
even after unregistration. This may lead to unbounded increase of memory
use if new event targets are allocated to new memory locations.
ported: c960360106

src/lib/base/EventQueue.cpp

@@ -274,6 +274,9 @@ void EventQueue::removeHandler(EventTypes type, void *target)
     if (index2 != typeHandlers.end()) {
       typeHandlers.erase(index2);
     }
+    if (typeHandlers.empty()) {
+      m_handlers.erase(index);
+    }
   }
 }
 
@@ -282,7 +285,7 @@ void EventQueue::removeHandlers(void *target)
   std::scoped_lock lock{m_mutex};
   HandlerTable::iterator index = m_handlers.find(target);
   if (index != m_handlers.end()) {
-    index->second.clear();
+    m_handlers.erase(index);
   }
 }