Right-click on Thunderbird account in folder tree shows an error in console

[RealRaven2000]

Right-clicking the account in folder tree, using quickFilters 6.11, shows the following error in console:

WebExtensions: getApplyIncomingFilters failed: NS_ERROR_FAILURE: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIMsgFolder.getStringProperty]
    getApplyIncomingFilters jar:file:///I:/Thunderbird_Profiles/ct4akusa.Beta-Test/extensions/quickFilters@axelg.com.xpi!/chrome/content/api/Utilities/implementation.js:149
    result resource://gre/modules/ExtensionParent.sys.mjs:1223
    withCallContextData resource://gre/modules/ExtensionParent.sys.mjs:666
    result resource://gre/modules/ExtensionParent.sys.mjs:1222
    withPendingBrowser resource://gre/modules/ExtensionParent.sys.mjs:676
    result resource://gre/modules/ExtensionParent.sys.mjs:1221
    callAndLog resource://gre/modules/ExtensionParent.sys.mjs:1172
    recvAPICall resource://gre/modules/ExtensionParent.sys.mjs:1220
implementation.js:151

this happens during the call to getApplyIncomingFilters() - which is used to toggle the popup menu item "Apply filters automatically". Found this issue while testing for #355