"Column to predict (Label)" not populated

**System Information (please complete the following information):**
- Model Builder Version (available in Manage Extensions dialog): 17.15.0.2337001
- Visual Studio Version: 17.10.1

**Describe the bug**
- On which step of the process did you run into an issue: I tried following the guide here https://dotnet.microsoft.com/en-us/learn/ml-dotnet/get-started-tutorial/data. Chose the yelp_labelled.txt file, "Data Preview" is populated.
- Clear description of the problem: The drop-down menu "Column to predict (Label)" only contains "Select column" and not "col0", "col1" as expected. Since I cannot select a column to predict, I can't continue to the next step in the guide.

**To Reproduce**
Steps to reproduce the behavior:
1. Follow the steps in https://dotnet.microsoft.com/en-us/learn/ml-dotnet/get-started-tutorial/data
2. Selecting "Column to predict (Label)" is not possible

**Expected behavior**
I expected the "Column to predict (Label)" to be populated with the items "col0" and "col1"

**Screenshots**

Beginne damit, dem verknüpften Data-Tutorial in Model Builder mit yelp_labelled.txt zu folgen, und reproduziere das leere Menü "Column to predict (Label)", nachdem Data Preview geladen wurde. Erledigt ist es, wenn das Menü col0 und col1 enthält und der Workflow mit dem nächsten Schritt fortfahren kann.

Vom Indexierungsmodell aus dem Issue-Text verfasst.