fixed broken fonts on Firefox

lib/single-file/rules-minifier.js

@@ -66,11 +66,11 @@ this.rulesMinifier = this.rulesMinifier || (() => {
 		let stylesheetContent = "";
 		if (rules) {
 			Array.from(rules).forEach(rule => {
-				if (rule.media) {
+				if (rule.type == CSSRule.MEDIA_RULE) {
 					stylesheetContent += "@media " + Array.prototype.join.call(rule.media, ",") + " {";
 					stylesheetContent += processRules(doc, rule.cssRules, rulesData);
 					stylesheetContent += "}";
-				} else if (rule.selectorText) {
+				} else if (rule.type == CSSRule.STYLE_RULE) {
 					const selector = getFilteredSelector(rule.selectorText);
 					if (selector) {
 						try {
@@ -79,6 +79,7 @@ this.rulesMinifier = this.rulesMinifier || (() => {
 								rulesData.selectors.add(selector);
 								if (rule.style && rule.style.fontFamily) {
 									rule.style.fontFamily.split(",").forEach(fontFamily => rulesData.fonts.used.add(getFontFamily(fontFamily)));
+									rule.style.fontFamily.split(",").forEach(fontFamily => console.log("used", getFontFamily(fontFamily)));
 								}
 							}
 						} catch (error) {
@@ -86,8 +87,10 @@ this.rulesMinifier = this.rulesMinifier || (() => {
 						}
 					}
 				} else {
-					if (rule.type == CSSRule.FONT_FACE_RULE && rule.style && rule.style.fontFamily) {
-						rulesData.fonts.declared.add(getFontFamily(rule.style.fontFamily));
+					const fontFamily = rule.style && rule.style.getPropertyValue("font-family");
+					if (rule.type == CSSRule.FONT_FACE_RULE && rule.style && fontFamily) {
+						rulesData.fonts.declared.add(getFontFamily(fontFamily));
+						console.log("declared", getFontFamily(fontFamily));
 					}
 					stylesheetContent += rule.cssText;
 				}
@@ -100,11 +103,12 @@ this.rulesMinifier = this.rulesMinifier || (() => {
 		let stylesheetContent = "";
 		if (rules) {
 			Array.from(rules).forEach(rule => {
+				const fontFamily = rule.style && rule.style.getPropertyValue("font-family");
 				if (rule.media) {
 					stylesheetContent += "@media " + Array.prototype.join.call(rule.media, ",") + " {";
 					stylesheetContent += deleteUnusedFonts(doc, rule.cssRules, unusedFonts);
 					stylesheetContent += "}";
-				} else if (rule.type != CSSRule.FONT_FACE_RULE || (rule.type == CSSRule.FONT_FACE_RULE && rule.style && rule.style.fontFamily && !unusedFonts.includes(getFontFamily(rule.style.fontFamily)))) {
+				} else if (rule.type != CSSRule.FONT_FACE_RULE || (rule.type == CSSRule.FONT_FACE_RULE && rule.style && fontFamily && !unusedFonts.includes(getFontFamily(fontFamily)))) {
 					stylesheetContent += rule.cssText;
 				}
 			});