FieldsetLayout: Hide header when there is no icon or label
FieldsetLayout: Hide header when there is no icon or label

Bug: T180535
Change-Id: I79fe95e32272f013a1ce4e48a811fa9fbb53f4e6

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui