Populate includes field in library.properties
The includes field in library.properties is used to specify which #include directives should be added to the sketch via Sketch > Include Library > LIBRARYNAME. Leaving this field empty causes that action to add the following line to the sketch:
#include <>
which results in a compilation error.
Reference:
https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification#libraryproperties-file-format