I got something similar. when I attach a wire from my combinator to the train stop, i have train network selected and this stop is fuel depot in my combinator when it happens.
The mod LTN Manager (0.5.0) caused a non-recoverable error.
Please report this error to the mod author.
Error while running event LtnManager::on_lua_shortcut (ID 42)
Unknown sprite "flib_indicator_grey"
stack traceback:
[C]: in function 'newindex'
__LtnManager/lib/gui.lua:189: in function 'recursive_update'
LtnManager/lib/gui.lua:244: in function 'recursive_update'
LtnManager/lib/gui.lua:244: in function 'recursive_update'
LtnManager/lib/gui.lua:252: in function 'update'
LtnManager/scripts/gui/stations.lua:125: in function 'update'
LtnManager/scripts/gui/index.lua:128: in function 'update'
LtnManager/scripts/gui/index.lua:34: in function 'open'
LtnManager/scripts/gui/index.lua:60: in function 'toggle'
LtnManager/control.lua:190: in function <LtnManager/control.lua:182>