Tweaks and fixes

• Delete a job that was previously invoiced would fail with a 'save mode not defined' error. Now fixed
• Subtle rounding issues in some circumstances involving certain spares discounts & c9 setup where spares rounding is set to 0.00. Would trigger journal balance errors. Now fixed. Non update workaround involves reconfiguring c9 so it rounds to 0.01 (which is what 0.00 is functionally supposed to be equivalent to).