Don't reuse the '$matches' array in 'RSSUtils::decode_srcset()'.

This causes the size of the array to be incorrectly doubled due to the original regex match items being combined with the custom items (i.e. the ones with just 'url' and 'size' keys).

Also rework 'RSSUtils::encode_srcset()' a bit so it looks similar to 'RSSUtils::decode_srcset()'.

classes/RSSUtils.php

@@ -2074,27 +2074,14 @@ class RSSUtils {
 			$srcset, $matches, PREG_SET_ORDER
 		);
 
-		foreach ($matches as $m) {
-			array_push($matches, [
-				"url" => trim($m["url"]),
-				"size" => trim($m["size"])
-			]);
-		}
-
-		return $matches;
+		return array_map(fn(array $m) => ['url' => trim($m['url']), 'size' => trim($m['size'])], $matches);
 	}
 
 	/**
 	 * @param array<int, array<string, string>> $matches An array of srcset subitem arrays with keys "url" and "size"
 	 */
 	static function encode_srcset(array $matches): string {
-		$tokens = [];
-
-		foreach ($matches as $m) {
-			array_push($tokens, trim($m["url"]) . " " . trim($m["size"]));
-		}
-
-		return implode(",", $tokens);
+		return implode(',', array_map(fn(array $m) => trim($m['url']) . ' ' . trim($m['size']), $matches));
 	}
 
 	static function function_enabled(string $func): bool {