bugs

• Possible NPD with frontsector of line_t (18 Sep 2021 | Tags phase-1-bugs, bugs, phase-1)
• OOB array reads in R_DrawColumn (18 Sep 2021 | Tags phase-1-bugs, bugs, phase-1)
• UB with pointer to one-before-first of array (16 Sep 2021 | Tags phase-1-bugs, bugs, phase-1)