2504007 - Unhandled Error (HTTP Status:500 unmarshal.invalid.xml) when validating script logic and ABAP Runtime error OBJECTS_OBJREF_NOT_ASSIGNED_NO CX_SY_REF_IS_INITIAL

The following error occurs when clicking the "Validate" button to check the script logic structure:

Unhandled Error (HTTP Status:500 unmarshal.invalid.xml)

Also, the following ABAP Runtime error (short dump) occurs in transaction code ST22:

Category ABAP Programming Error
Runtime Errors OBJECTS_OBJREF_NOT_ASSIGNED_NO
Except. CX_SY_REF_IS_INITIAL
ABAP Program CL_UJK_MODEL==================CP
Application Component EPM-BPC-NW-ADM-LF

Short Text: Access using a 'ZERO' object reference is not possible.

What happened? Error in the ABAP Application Program

The current ABAP program "CL_UJK_MODEL==================CP" had to be terminated because it has come across a statement that unfortunately cannot be executed.

Error analysis: An exception has occurred which is explained in more detail below.

The exception is assigned to class 'CX_SY_REF_IS_INITIAL' and was not caught in procedure "GET_CHILDREN" "(METHOD)", nor was it propagated by a RAISING clause.

"OBJECTS_OBJREF_NOT_ASSIGNED_NO" CX_SY_REF_IS_INITIAL
"CL_UJK_MODEL==================CP" bzw. CL_UJK_MODEL==================CM00J
"GET_CHILDREN"

>>>>>   lo_hier->get_children(

This error below may also appear in a data manager (DM) import package log before validating the script logic (note the DM package runs script logic):

An exception with the type CX_SY_REF_IS_INITIAL occurred, but was neither handled locally, nor declared in a RAISING clause.

Dereferencing of the Null reference.

Ocorreu um exceção do tipo CX_SY_REF_IS_INITIAL, mas ela não foi tratada localmente nem declarada por meio de uma cláusula RAISING. 
Anular referência da referência NULL.

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EPM, BPC  NW, Business Planning and Consolidation for NetWeaver, SAP BPC FOR NetWeaver, BPCNW, Embedded, standard, classic, unified, BOPC,  Nm.tarefa LOAD INFOPROVIDER: Ocorreu um exceção do tipo CX_SY_REF_IS_INITIAL, mas ela não foi tratada localmente nem declarada por meio de uma cláusula RAISING. Anular referência da referência NULL. , KBA , EPM-BPC-NW , NetWeaver Version , BW-PLA-BPC , BPC 'embedded model' , How To