CMCD requests via query-string end with a superfluous comma

[mgreve-akamai]

Environment

• The MPD passes the DASH-IF Conformance Tool on https://conformance.dashif.org/
• The stream has correct Access-Control-Allow-Origin headers (CORS)
• There are no network errors such as 404s in the browser console when trying to play the stream
• The issue observed is not mentioned on https://github.com/Dash-Industry-Forum/dash.js/wiki/FAQ
• The issue occurs in the latest reference client on http://reference.dashif.org/dash.js/ and not just on my page

• Link to playable MPD file: Irrelevant
• Dash.js version: Newest nightly on Aug 25, 2021 (https://reference.dashif.org/dash.js/nightly/dist/dash.all.debug.js)
• Browser name/version: Irrelevant
• OS name/version: Irrelevant

Steps to reproduce

Play the stream on the CMCD sample page: https://reference.dashif.org/dash.js/nightly/samples/advanced/cmcd.html

Observed behavior

All CMCD requests ends with a superfluous comma. Here's one example with the superfluous comma highlighted: https://dash.akamaized.net/akamai/bbb_30fps/bbb_30fps_480x270_600k/bbb_30fps_480x270_600k_1.m4v?CMCD=bl%3D0%2Cbr%3D759%2Ccid%3D%2221cf726cfe3d937b5f974f72bb5bd06a%22%2Cd%3D4000%2Cdl%3D0%2Cnor%3D%22%2Fakamai%2Fbbb_30fps%2Fbbb_30fps_480x270_600k%2Fbbb_30fps_480x270_600k_2.m4v%22%2Cot%3D%22v%22%2Crtp%3D30400%2Csf%3D%22d%22%2Csid%3D%22b248658d-1d1a-4039-91d0-8c08ba597da5%22%2Cst%3D%22v%22%2Csu%2Ctb%3D14932**%2C**

Here's the decoded variant:
https://dash.akamaized.net/akamai/bbb_30fps/bbb_30fps_480x270_600k/bbb_30fps_480x270_600k_1.m4v?CMCD=bl=0,br=759,cid="21cf726cfe3d937b5f974f72bb5bd06a",d=4000,dl=0,nor="/akamai/bbb_30fps/bbb_30fps_480x270_600k/bbb_30fps_480x270_600k_2.m4v",ot="v",rtp=30400,sf="d",sid="b248658d-1d1a-4039-91d0-8c08ba597da5",st="v",su,tb=14932,

The last %2C% (comma) part is not needed.

Console output

Irrelevant

Expected behavior

The comma is not needed.

[dsilhavy]

Fixed in #3745