Eric - you defined a [[StandardReport]] but did not tell the report generator where to find the skin.conf file in the appropriate subdirectory under the /etc/weewx/skins directory.
To have that report known to the report generator, but skipped, simply set enable=false ala:
[[StandardReport]]
skin = Standard
enable = false
To undefine that report completely, you could have commented it 'all' out ala:
# skin = Standard
# enable = false
But your half-way variant is not valid. Leave it uncommented and enable=false, or comment the whole report definition out completely. The half-way measure you tried is not valid.