csrf: Improve API for when no CSRF input is available.
csrf: Improve API for when no CSRF input is available.

Since we're adding this to a large number of portico pages, there's no
guarantee that these pages actually have a CSRF input.

Though given that the logout template contains a CSRF input,
realistically it should always be present.

showell/zulip,dhcrzf/zulip,synicalsyntax/zulip,kou/zulip,hackerkid/zulip,tommyip/zulip,dhcrzf/zulip,brainwane/zulip,tommyip/zulip,synicalsyntax/zulip,kou/zulip,eeshangarg/zulip,hackerkid/zulip,shubhamdhama/zulip,rishig/zulip,hackerkid/zulip,timabbott/zulip,timabbott/zulip,synicalsyntax/zulip,tommyip/zulip,punchagan/zulip,synicalsyntax/zulip,dhcrzf/zulip,andersk/zulip,tommyip/zulip,tommyip/zulip,dhcrzf/zulip,dhcrzf/zulip,andersk/zulip,brainwane/zulip,zulip/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,eeshangarg/zulip,eeshangarg/zulip,showell/zulip,punchagan/zulip,rht/zulip,timabbott/zulip,brainwane/zulip,synicalsyntax/zulip,kou/zulip,showell/zulip,shubhamdhama/zulip,rishig/zulip,eeshangarg/zulip,punchagan/zulip,shubhamdhama/zulip,punchagan/zulip,zulip/zulip,showell/zulip,andersk/zulip,synicalsyntax/zulip,hackerkid/zulip,brainwane/zulip,timabbott/zulip,shubhamdhama/zulip,rishig/zulip,andersk/zulip,hackerkid/zulip,rishig/zulip,rishig/zulip,brainwane/zulip,zulip/zulip,tommyip/zulip,shubhamdhama/zulip,rht/zulip,rishig/zulip,showell/zulip,zulip/zulip,rishig/zulip,eeshangarg/zulip,andersk/zulip,timabbott/zulip,brainwane/zulip,punchagan/zulip,shubhamdhama/zulip,andersk/zulip,zulip/zulip,shubhamdhama/zulip,hackerkid/zulip,dhcrzf/zulip,timabbott/zulip,punchagan/zulip,kou/zulip,rht/zulip,tommyip/zulip,punchagan/zulip,eeshangarg/zulip,showell/zulip,rht/zulip,timabbott/zulip,zulip/zulip,brainwane/zulip,rht/zulip,rht/zulip,showell/zulip,andersk/zulip,rht/zulip,kou/zulip,kou/zulip,dhcrzf/zulip,synicalsyntax/zulip,zulip/zulip