Empty row in annotation panel shown when alignment first imported

Jalview attempts to automatically set the annotation panel height to show just the annotations present on the alignment and at least one sequence. JAL-4392's 'autohide' mechanism configures the visibility of calculation based annotation rows according to whether data is available.

In 2.11.4.0, and 2.11.4.1, importing a bare fasta protein sequence alignment results in an empty row is shown where jalview calculates the height of the alignment panel *including* the protein secondary structure annotation consensus row, but this is then hidden.