Assertion: 13111:wrong type for field 3 != 4 - MongoDB C++ driver -

in mongodb database have documents of form:

   {    "timestamp" : "2012-01-15t17:56:14.85",         "event" : [             {                 "id" : "1851236846",                 "qualifier_id" : "209"             },             {                 "id" : "378258775",                 "qualifier_id" : "57",                 "value" : "1"             }         ]     }     {   "timestamp" : "2012-01-15t16:06:09.378"     } 

some of them contain array event don't.

when i'm trying process data using c++ mongodb driver 2.4:

 while (cursor->more()) {    bsonobj bo = cursor->next();   cout << "timestamp: " << bo.getstringfield("timestamp") << std::endl;    if(bo.haselement("event")) {     cout<<"here"<< endl;      std::vector<bsonelement> = bo.getfield("event").array(); // ---> @ line breaks!!      (unsigned int j = 0; j < be.size(); j++) {                bsonobj bo2 = be[j].embeddedobject();               cout << "qualifier id: " << bo2.getstringfield("qualifier_id") << std::endl;               cout << "value: " << bo2.getstringfield("value")<< std::endl;      }   } 

i error:

  timestamp: 2012-01-15t16:06:06.529    here    qualifier id: 15    value:      qualifier id: 56    value:    timestamp: 2012-01-15t16:06:07.560    here    qualifier id: 212    value: 14.6     qualifier id: 141    value: 89.2     qualifier id: 213    value: 5.9     qualifier id: 56    value:     qualifier id: 140    value: 46.7    timestamp: 2012-01-15t16:06:09.378   here   sun jul 21 20:06:16.974 assertion: 13111:wrong type field (event) 3 != 4   caught wrong type field (event) 3 != 4 

in conclusion condition bo.haselement("event") true.(???) program brakes here:

   std::vector<bsonelement> = bo.getfield("event").array(); 

when array event has no members.

pease help!

i can more info error: http://docs.mongodb.org/manual/reference/operator/type/#op._s_type 3 => object 4 => array