Clicking on the first commit in a shallow clone repository causes a hang

Steps to reproduce:

• Clone any git repository and specify clone depth greater than zero (shallow clone)
• Open the cloned repository Log/History view
• Scroll down to the very first commit and click on it
• Observer SourceTree application hang and runaway memory leak

This may be caused by the fact that in a shallow clone the very first commit in a repository refers to a parent commit which has not been fetched from the server.