Curious Error, would like to know what is causing it?

const char *SimObject::getPrefixedDataField(StringTableEntry fieldName, const char *array)
{
    // Sanity!
    AssertFatal( fieldName != NULL, "Cannot get field value with NULL field name." );

    // Fetch field value.
    const char* pFieldValue = getDataField( fieldName, array );

    // Sanity.
    AssertFatal( pFieldValue != NULL, "Field value cannot be NULL." );

    // Return without the prefix if there's no value.
    if ( *pFieldValue == 0 )
        return StringTable->EmptyString;

    // Fetch the field prefix.
    StringTableEntry fieldPrefix = getDataFieldPrefix( fieldName );

    // Sanity!
    AssertFatal( fieldPrefix != NULL, "Field prefix cannot be NULL." );

    // Calculate a buffer size including prefix.
    const U32 valueBufferSize = dStrlen(fieldPrefix) + dStrlen(pFieldValue) + 1;

    // Fetch a buffer.
    char* pValueBuffer = Con::getReturnBuffer( valueBufferSize );

    // Format the value buffer.
    dSprintf( pValueBuffer, valueBufferSize, "%s%s", fieldPrefix, pFieldValue );

    return pValueBuffer;
}

if(!isObject(GuiDefaultProfile)) new GuiControlProfile (GuiDefaultProfile)
{
Modal = true;
};  

new GuiControl(Nope)
{
	Name="Nope";
	Profile="GuiDefaultProfile";
    HorizSizing="relative";
    VertSizing="relative";
    Position="0 0";
    Extent="1024 30";
    MinExtent="220 30";
    Visible="1";
};

%taml = new Taml()
{
	WriteDefaults = true;
	Format = Xml;
};
%taml.write(Nope, "./log.gui.taml");
%taml.delete();