error: control reaches end of non-void function

[jimjones48]

Using the ID20Reader Library with an ESP8266 board, I get the error:

C:\arduino-1.8.16\portable\sketchbook\libraries\ID20Reader\ID20Reader.cpp: In member function 'String ID20Reader::get()':
C:\arduino-1.8.16\portable\sketchbook\libraries\ID20Reader\ID20Reader.cpp:108:1: error: control reaches end of non-void function [-Werror=return-type]
108 | }
| ^
cc1plus.exe: some warnings being treated as errors

Using Arduino IDE 1.8.16