search: crash when navigating map after searching k sidebar

[lethosor]

Reported by Fleeting Flames (via Kitfox Discord)

To reproduce:

1. With k, select a tile with at least 3 items listed in the sidebar (floors/walls included)
2. Search and narrow down the list to under 3 items (e.g. s, beer, Enter)
3. Navigate away from this tile with a key that has an ASCII representation (<, >, or 1-9 - not an arrow key), or with F1-F8 hotkeys (edit: the crash with hotkeys seems to occur when they are used in step 3, followed by arrow keys in step 4)
4. Navigate to an unrevealed tile (or maybe a tile with fewer items than in step 2?) with the arrow keys (or via an announcement, etc.)

Step 4 usually crashes because the search state isn't cleared in step 3 due to the check added in 87b1524.

The logic in one of these places should probably change:

dfhack/plugins/search.cpp

Line 1956 in a723249

if (cursor_key_pressed(input))

dfhack/plugins/search.cpp

Line 121 in a723249

for (auto it = input->begin(); it != input->end(); ++it)

We only need to intercept ASCII keys when the search field is active (step 2).

Note that changing the behavior of cursor_key_pressed may also affect the behavior of search_generic, so the proper fix here might be complicated:

dfhack/plugins/search.cpp

Line 252 in a723249

else if (cursor_key_pressed(input))