Changed the redundant check against fRate with a test against fPrice as
everywhere else in the file.
Also change some comparisons against 0.0 instead of 0 when using floating
point variable (to be consistent with the rest of the code).

Change-Id: I94a397f1578a90156359987996cb1ef02d5e4209
Reviewed-on: https://gerrit.libreoffice.org/779Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>