fix bug with TextViewer instance in debug mode, appears after transferring new program on PLC
TextViewer isn't able to display debug values, so calling for this class SubscribeAllDataConsumers method causes error

[TOPOLOGY]
NetName=None
Nodes=0x01
Node2Present=0x01
Node2Name=SlaveNode
Node2DCFName=Slave_0_0.eds
EDSBaseName=eds