closes https://github.com/assimp/assimp/issues/1340: Fix handling of empty nodes in openddl-parser.

contrib/openddlparser/code/OpenDDLParser.cpp

@@ -100,9 +100,15 @@ static bool isUnsignedIntegerType( Value::ValueType integerType ) {
 }
 
 static DDLNode *createDDLNode( Text *id, OpenDDLParser *parser ) {
+    // Basic checks
     if( ddl_nullptr == id || ddl_nullptr == parser ) {
         return ddl_nullptr;
     }
+    
+    // If the buffer is empty ( an empty node ) return nullptr
+    if ( ddl_nullptr == id->m_buffer ) {
+        return ddl_nullptr;
+    }
 
     const std::string type( id->m_buffer );
     DDLNode *parent( parser->top() );