[ubuntu] Possible problem with flash plugin update in 16.04

Software updater showed a Adobe flash plugin update. I did that. Was then asked to reboot. After that everything seemed fine, no messages.
Then I started an app with gksu in terminal. All of a sudden some text appears in the terminal:

1463085977937 addons.update-checker WARN Update manifest for [email protected] did not contain an updates property
1463085978016 addons.update-checker WARN Update manifest for [email protected] did not contain an updates property
1463085978101 addons.update-checker WARN Update manifest for {972ce4c6-7e08-4474-a285-3208198ce6fd} did not contain an updates property
1463085978241 addons.update-checker WARN Update manifest for [email protected] did not contain an updates property
1463085981969 addons.xpi ERROR Failed to clean updated system add-ons directories.: Unix error 2 during operation DirectoryIterator.prototype.next on file /root/.mozilla/firefox/9egkwca3.default/features (No such file or directory) ((unknown module)) No traceback available
1463085990120 addons.xpi ERROR Attempted to load bootstrap scope from missing directory /root/.mozilla/firefox/9egkwca3.default/extensions/[email protected]
1463085990120 addons.xpi WARN Add-on [email protected] is missing bootstrap method shutdown
1463085990123 addons.manager WARN Exception calling callback: [Exception... "Component retued failure code: 0x80520006 (NS_ERROR_FILE_TARGET_DOES_NOT_EXIST) [nsIFile.isDirectory]" nsresult: "0x80520006 (NS_ERROR_FILE_TARGET_DOES_NOT_EXIST)" location: "JS frame :: resource://gre/modules/addons/XPIProvider.jsm :: getURIForResourceInFile :: line 1506" data: no] Stack trace: getURIForResourceInFile()@resource://gre/modules/addons/XPIProvider.jsm:1506 < this.XPIProvider.callBootstrapMethod()@resource://gre/modules/addons/XPIProvider.jsm:4668 < this.XPIProvider.uninstallAddon()@resource://gre/modules/addons/XPIProvider.jsm:4921 < AddonWrapper.prototype.uninstall()@resource://gre/modules/addons/XPIProvider.jsm:7129 < uninstallHotfix/<()@resource://gre/modules/addons/XPIProvider.jsm -> jar:file:///root/.mozilla/firefox/9egkwca3.default/extensions/[email protected]!/bootstrap.js:78 < safeCall()@resource://gre/modules/AddonManager.jsm:179 < makeSafe/<()@resource://gre/modules/AddonManager.jsm:195 < Handler.prototype.process()@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:933 < this.PromiseWalker.walkerLoop()@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:812 < this.PromiseWalker.scheduleWalkerLoop/<()@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:746
1463086090082 addons.xpi WARN Add-on [email protected] is missing bootstrap method shutdown

Question 1: Why did it appear in the terminal?

Question(s) 2: Should I do something? What does it all mean, Powers?