fix wrong embed type reporting

Author: Bart Veneman

src/stylesheet/stylesheet.js

@@ -1,12 +1,16 @@
-export function getEmbedType(embed) {
+export function getEmbedType(/** @type string */embed) {
 	// data:image/gif;base64,R0lG
-	var start = 5 // `data:`.length
-	var semicolon = embed.indexOf(';')
+	let start = 5 // `data:`.length
+	let semicolon = embed.indexOf(';')
+	let comma = embed.indexOf(',')
 
 	if (semicolon === -1) {
-		var comma = embed.indexOf(',')
 		return embed.substring(start, comma)
 	}
 
+	if (comma !== -1 && comma < semicolon) {
+		return embed.substring(start, comma);
+	}
+
 	return embed.substring(start, semicolon)
 }

src/stylesheet/stylesheet.test.js

@@ -188,6 +188,7 @@ Stylesheet('correctly extracts embed types', () => {
     ['application/font-woff', 'data:application/font-woff;base64,d09GRgAB'],
     ['font/opentype', 'data:font/opentype;base64,T1RUTwAJAIAAAw'],
     ['image/png', 'data:image/png;base64,iVBORw0KGgoAAAANS'],
+    ['image/svg+xml', `data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 28.84 26.6'%3E%3Cdefs%3E%3Cstyle%3E.cls-1%7Bfill:%23e93e32;%7D%3C/style%3E%3C/defs%3E%3Ctitle%3EArtboard 29%3C/title%3E%3Cpath class='cls-1' d='M3.29,2.73a66.7,66.7,0,0,0,3.21,9.52l6.29,1.08L8.1,15.53c2.91,5.28,7,9.09,12.14,4.55L25,24.52l.57-.52-3.83-5.48c3.6-4.32,1.74-7.76-1.93-10.36L17,13.29l-.1-6.85A43.83,43.83,0,0,0,11,4L9,7.7,9,3.39c-2.2-.65-4.07-1.08-5.08-1.3A.52.52,0,0,0,3.29,2.73Z'/%3E%3C/svg%3E`]
   ].forEach(([expected, fixture]) => {
     assert.is(getEmbedType(fixture), expected)
   })