As sated above you need to "Edit or add library.properties to that folder so that you specify a valid category."
This link has some good info on the structure of the file: https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification
From that link:
library.properties file format
The library.properties file is a key=value properties list. Every field in this file is UTF-8 encoded. The available fields are:
**name** - the name of the library
version - version of the library. Version should be semver compliant. 1.2.0 is correct; 1.2 is accepted; r5, 003, 1.1c are invalid
**author** - name/nickname of the authors and their email addresses (not mandatory) separated by comma ","
**maintainer** - name and email of the maintainer
**sentence** - a sentence explaining the purpose of the library
**paragraph** - a longer description of the library. The value of sentence always will be prepended, so you should start by writing the second sentence here
**category** - if present, one of these: "Display", "Communication", "Signal Input/Output", "Sensors", "Device Control", "Timing", "Data Storage", "Data Processing", "Other"
**url** - the URL of the library project, for a person to visit. Can be a github or similar page as well
architectures - a comma separated list of architectures supported by the library. If the library doesn’t contain architecture specific code use “*” to match all architectures
**dot_a_linkage** - (available from IDE 1.6.0 / arduino-builder 1.0.0-beta13) when set to true, the library will be compiled using a .a (archive) file. First, all source files are compiled into .o files as normal. Then instead of including all .o files in the linker command directly, all .o files are saved into a .a file, which is then included in the linker command.
**includes** - (available from IDE 1.6.10) a comma separated list of files to be added to the sketch as #include <...> lines. This property is used with the "Include library" command in the IDE. If the property is undefined all the headers files (.h) on the root source folder are included.