ensure range is defined

Former-commit-id: c5981e56ec6c7ad0a05eeeb33b23cc0df2f50fdc

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

@@ -317,7 +317,7 @@ this.singlefile.lib.modules.fontsMinifier = this.singlefile.lib.modules.fontsMin
 						const secondRange = firstRange;
 						regExpString = "[" + firstRange.replace(REGEXP_QUESTION_MARK, "0") + "-" + secondRange.replace(REGEXP_QUESTION_MARK, "F") + "]";
 
-					} else {
+					} else if (range[0]) {
 						regExpString = "[" + transformRange(range[0]) + "]";
 					}
 				}