It doesn't make sense for us to track a separate current filter when
it should just the be filter of current message list if there is one.
This will reduce possible confusion in the codebase where filter
returned by narrow_state is different from message_lists.current.
For spectators, the chunk of page_params that originates from
do_events_register isn’t assigned until ui_init.js. That means the
TypeScript type of page_params is mostly a lie during module load
time: reading a parameter too early silently results in undefined
rather than the declared type, with unpredictable results later on.
We want to make such an early read into an immediate runtime error,
for both users and spectators consistently, and pave the way for
runtime validation of the page_params type. As a second step, split
out the subset of fields that pertain to the entire realm.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
All message view has `in-home` filter and is not empty.
If there are no terms provided, we set filter to display
all messages (including muted streams/topics).
We make it mandatory to provide terms to Filter.