Check if debugMode is defined before using it
Check if debugMode is defined before using it

Else the sabre error page (where the var is not defined) will throw
warnings all the time.

Signed-off-by: Roeland Jago Douma <982d370f7dc34a05b4abe8788f899578d515262d@famdouma.nl>

nextcloud/server,nextcloud/server,nextcloud/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,nextcloud/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,andreas-p/nextcloud-server