The mod What is it really used for? caused a non-recoverable error.
Please report this error to the mod author.
When I search the menu bar (typing, not using item), after I type the second letter (when the suggestions begin to show up), the error shown below gets thrown.

Error while running event what-is-it-really-used-for::on_string_translated (ID 147)
what-is-it-really-used-for/control.lua:963: table index is nil
stack traceback:
what-is-it-really-used-for/control.lua:963: in function <what-is-it-really-used-for/control.lua:961>

Can you tell me what other mods you are using?

Just updated to latest version, all other mods the same. Got new error message

Error while running event what-is-it-really-used-for::on_string_translated (ID 147)
what-is-it-really-used-for/control.lua:1010: table index is nil
stack traceback:
what-is-it-really-used-for/control.lua:1010: in function <what-is-it-really-used-for/control.lua:1008>

Now for the mods. All are at latest version.

Factorio 0.18.3

Advanced Furnaces
AutoTrash
Base
Belt Buffer 0.18
Bottleneck
Bulk Teleporters
Carbon Capture
Concretexture
Construction Drones
Death Markers
Deep Mine
Dirt Path
Disco Science
Electric Furnaces
Even Distribution
Factorio Standard Library
Flow Control
Force Fields
FARL
Glowing laser beams
Heat Glow
HermiosLibs
How far has it been?
Hydrogen power systems
Induction Charging
Land Mine thrower
Laser Lines
Lighted electric poles +
Loader Redux
Logistic Cargo Wagon
Lovely_santa's library of knowledge
LTN
Mining drones
Modular turrets
Module inserter
Noxys waterfill
Optera's library
Rail Power system
Raven
Recursive Blueprints
Reinforced walls
Reverse Factory
Robocharger
Robosubstation
Robot tree farm
Shield FX
Squeak Through
Storage tank MK2
The ruins mod
Turbwhine
Turret Shields
Unit Control
VortiK's Deep core mining
Walls block spitters
Warehousing mod
What is it really used for?
Where is my body?
Wire shortcuts

... I realize I may have a lot of mods enabled.

I've tracked this down to interaction with "Construction Drones", where localised_name is defined as a simple string and not an array/LocalisedString.

As it's a shortcut other mods may take as well, this could be an solution for the time being:

script.on_event(defines.events.on_string_translated, function(event)
local localised_string = event.localised_string[1] or event.localised_string
translations = global.wiiuf_item_translations[event.player_index]
translations[localised_string] = event.result
end)

Thanks, that helped me fix much faster. Should be resolved in 1.5.5.