[bug] Object is possibly 'undefined'

[DerekNonGeneric]

These issues were raised via CI run: https://github.com/openinf/util-object/actions/runs/3258038095/jobs/5349784833/

src/index.ts:138:19 - error TS2532: Object is possibly 'undefined'.

138     if (o1[k] !== o2[k]) {
                      ~~

src/index.ts:143:19 - error TS2532: Object is possibly 'undefined'.

143     if (o2[k] !== o1[k]) {
                      ~~


Found 2 errors in the same file, starting at: src/index.ts:138

This may be the (most likely) reason: a013a28#commitcomment-86935693.