fixed typo

lib/single-file/css-fonts-alt-minifier.js

@@ -67,7 +67,7 @@ this.fontsAltMinifier = this.fontsAltMinifier || (() => {
 				stats.rules.discarded += cssRules.getSize();
 				if (stylesheetInfo.mediaText && stylesheetInfo.mediaText != MEDIA_ALL) {
 					const mediaFontsDetails = createFontsDetailsInfo();
-					mediaFontsDetails.medias.set("media-" + sheetIndex + "-" + stylesheetInfo.mediaText, mediaFontsDetails);
+					fontsDetails.medias.set("media-" + sheetIndex + "-" + stylesheetInfo.mediaText, mediaFontsDetails);
 					getFontsDetails(doc, cssRules, sheetIndex, mediaFontsDetails);
 				} else {
 					getFontsDetails(doc, cssRules, sheetIndex, fontsDetails);