[i496h] GUI JobWorker: extend 'try' coverage; rm special treatment for impossible case of no m_simulation ()

Merging branch 'i496h'  into 'r20.0'.

See merge request !1519

Merging branch 'msgs1'  into 'r20.0'.

See merge request !1521

Merging branch 'link_specular'  into 'r20.0'.

See merge request !1517

Merging branch 'hugofix'  into 'r20.0'.

See merge request !1514

Merging branch 'rm_src'  into 'r20.0'.

See merge request !1512

Merging branch 'release02'  into 'r20.0'.

See merge request !1510

[release01] Revise installation instructions; revise hugo config params; use shortcodes for URLs; repair broken links ()

Merging branch 'release01'  into 'r20.0'.

See merge request !1509