sentiment analysis example and text-processing nodes problem

Yesterday, I took a look at the sentiment analysis example and realised that thet there is a problem with the text-processing nodes and especially, strings to document node. When I execute the node, the document colon has no values but ("") -without parantheses-

I reset the nodes from the very beginning and then it worked. Then, I shut down the knime altogether and re-opened. There is that very problem again.

I have no idea what's going on in my computer. Except this text-processing and the flow variable error, everything seems to be working fine.