QHeaderView - change not needed if to Q_ASSERT

QHeaderView - change not needed if to Q_ASSERT

This removes an if that should always be false. If it isn't
false we had more logical indexes than sections.

Unless visualIndices and logicalIndices are both 0-sized
(meaning that visual and logical indexes are the same)
then they better have exactly as many indexes as sectionCount.
Otherwise there must be inconsistent data - some logicalindex
would refer to non-existing visual sections or some
visualindeces wouldn't be hit by logicalIndices.

Change-Id: I2dc92f40895438d912bba20612131baf63df4fbe
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>