This plug-in highlights characters such as non breakable space, characters that often break compilers and scripts and is almost impossible to spot in the editor.
To install this plug-in use package manager.
You might want to override the following parameters within your file settings:
highlight_unicode_max_file_size: Restrict this to a sane size in order not to DDOS your editor. Defaults to 1048576 (1 Mio).
highlight_unicode_color_name: Change this to a valid scope name, which has to be defined within your theme. Defaults to 'invalid'.