sidebar: Fix unread count shifted right in stream list.
sidebar: Fix unread count shifted right in stream list.

The reason for the bug was 71e3f778cc6c4024df8e44872aae953ded731892.
This commit makes the width 100% for selectable_sidebar_block only
on the right sidebar, the left sidebar selectable_sidebar_block
width is unset.

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