Fix delete() not returning sometimes, closes #1067

src/object/object_manager.cpp

@@ -71,7 +71,7 @@ bool CObjectManager::DeleteObject(CObject* instance)
         it->second.reset();
         m_shouldCleanRemovedObjects = true;
         return true;
-    }
+    } else assert(false);
 
     return false;
 }

src/script/scriptfunc.cpp

@@ -657,7 +657,7 @@ bool CScriptFunctions::rDelete(CBotVar* var, CBotVar* result, int& exception, vo
     }
 
     CObject* obj = CObjectManager::GetInstancePointer()->GetObjectById(rank);
-    if ( obj == nullptr )
+    if ( obj == nullptr || (obj->Implements(ObjectInterfaceType::Old) && dynamic_cast<COldObject*>(obj)->IsDying()) )
     {
         return true;
     }