Fix coverity issues (medium)
This MR fixes several medium-level issues found by Coverity Scan.
While less serious, medium-level issues are sometimes slightly more complex to fix because of code intent, and thus more prone to regressions than high-level issues.
Issues in SEP were set to ignore.
Some issues set to ignore based on code intent.
CID1445705 - unchecked cast in details table.
CID1445707 - unchecked fread returned bytes in StarComponent.
CID1445708 - unchecked cast in guider interface.
CID1445711 - unchecked cast in observing list.
CID1445714 - unchecked cast in details dialog.
CID1445719 - unchecked cast in details dialog.
CID1445721 - uninit var hfr in Analyze capture session.
CID1445725 - unchecked cast in EkosLive message.
CID1445726 - dead duplicated code in FITS packer.
CID1445728 - possible division by zero in Scheduler job time estimation.
CID1445729 - uninit var in Linear Focus.
CID1445730 - unchecked cast in EkosLive message.
CID1445734 - uninit vars in SchedulerJob.
CID1445742 - unintended sign extension in FITS star filtering.
CID1445743 - unchecked cast in EkosLive message.
CID1445748 - uninit vars in Meridian Flip test.
CID1445753 - stray semicolon in Capture test helper macro.
CID1445757 - fix if construct (sorry Akarsh).