scaled-font: Fix glyph and cluster count checks (CID #983386)
num_glyphs and num_clusters are explicitly checked to be non-NULL at the
beginning of this routine, and by this point in the code both have been
deref'd multiple times, so checking them for NULL here again is
superfluous.
It looks like the intent here is to verify the glyphs and clusters
arrays are non-NULL unless their counts are zero, so change the tests
accordingly.
Coverity ID: #983386
Signed-off-by: Bryce Harrington <bryce@bryceharrington.org>