Guider fixes: ra error plotting reversed, disabling axes bug

Addresses two of the bugs described in https://indilib.org/forum/general/10263-internal-guider-changes-please-read-if-you-use-it.html?start=12#75204

• RA error was negated in the guide tab's plot (not in analyze) but RA pulses were not negated. I removed the negating of RA error. (I might have alternatively negated the ra pulses.)

• The 'continue' statement in gmath.cpp::calculatePulses() which is executed when an axis is disabled was a bug. It prevented the code from reaching the line which set out_params.pulse_dir and out_params.pulse_length, and old values were used instead. Probably a long-standing bug, where likely (incorrect) guide pulses have been issued even though the axes were disabled.