Bug: placeholderdata keeps oldest non-null data

Placeholder data from treeDetails is storing the last time there was data, so if you change from commit 1 with data, go to commit 2 without data and then to a commit 3 without data as well, the transition from commit 2 to 3 will show the data from the first commit.

This is a visual bug, doesn't affect performance nor breaks the dashboard.

Issue found on #1117 