LinkedData component not robust to connectivity issues

[ewpatton]

Describe the bug

If you are not connected to the internet, the linked data component will cause a NPE when attempting to read data from the web. This kills the app.

Affects

• Designer
• Blocks editor
• Companion
• Compiled apps
• Buildserver
• Debugging
• Other... (please describe)

Expected behavior

The component should gracefully handle lack of connectivity rather than causing an app crash.

Steps to reproduce

Create an app to read a TTL file from the web. Compile and install the app. Disconnect from the network. Run the app and attempt to load the file. Observe crash message.