analysis: Add null check for dependent analysis

analysis: Add null check for dependent analysis

This fixes a NPE and also avoids execution the statistics analysis on
other trace types than LTTng Kernel when the view is open.

Change-Id: I6583dcbb80044586f25067f32a5fbd9f28c7d4ed
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/59045
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>