fdo#64337 Do not show empty findbar in startcenter.

Using the shortcut for search on the start center displayed an empty
toolbar on the start center. This commit adds a check to see whether
the command to execute in the startcenter is FocusToFindbar, and if
it is, it skips executing it.

Change-Id: I0835e87d4a1eef0fc9ff17c184b531592b3e2d5a