motifs tab makes first log line disappear

[bestchai]

To reproduce:

• Visualize a log
• Notice the first visible log line (blue '/timeline...' below):

• Click on motifs tab
• Click back on 'log lines' tab. Notice that the first log line disappeared:

The line re-appears when you hover over its space.

[Issue created by bestchai: 2015-08-22]