fix: PERIOD_FLATTENING_FAILED error with shaka 4.3.4 that did not occ…

…ur with shaka 3.1.2 shaka-project#5183  (shaka-project#5188)

Fixed handling of manifest with new codecs in later periods by adding
check for empty matchedStreams array in createNewOutputStrems()

Fixes shaka-project#5183

lib/util/periods.js

@@ -730,7 +730,7 @@ shaka.util.PeriodCombiner = class {
       // in advance.  concat() will add them to the output's MetaSegmentIndex.
     }
 
-    if (!outputStream.matchedStreams) {
+    if (!outputStream.matchedStreams || !outputStream.matchedStreams.length) {
       // This is not a stream we can build output from, but it may become part
       // of another output based on another period's stream.
       return null;