Broken "collapse" glyphs for code blocks

[mkroetzsch]

The IDE supports collapsing of multi-line blocks, e.g., if a rule spans several lines. The glyphs shown on the margin for collapse/uncollapse, however, are missing. This might relate to the following error that shows in the console when loading the page:

Content-Security-Policy: The page’s settings blocked the loading of a resource (font-src) at data:font/ttf;base64,AAEAAAALAIAAAwAwR1N… because it violates the following directive: “font-src 'self'”