fixed font name overwriting

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

@@ -163,6 +163,7 @@ this.singlefile.lib.modules.fontsMinifier = this.singlefile.lib.modules.fontsMin
 			test = testFontweight(fontWeight, usedFontWeights);
 			if (!test) {
 				usedFontWeights = optionalUsedFonts.map(fontInfo => {
+					fontInfo = Array.from(fontInfo);
 					fontInfo[2] = "normal";
 					return getUsedFontWeight(fontInfo, fontStyle, declaredFontsWeights);
 				});