custom button - toggle open new windows in background tabs

/*CODE*/
var prefManager = Components.classes["@mozilla.org/preferences-service;1"]
                    .getService(Components.interfaces.nsIPrefBranch);

// Available methods: getIntPref, getBoolPref, getCharPref
var current = prefManager.getBoolPref( "browser.tabs.loadDivertedInBackground" );

if ( current == false ) {
    // then tabs open in foreground
    prefManager.setBoolPref("browser.tabs.loadDivertedInBackground", true);
    document.querySelector("#custombuttons-button1").image = "data:image/png;base64,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";
} else {
    prefManager.clearUserPref("browser.tabs.loadDivertedInBackground");
    document.querySelector("#custombuttons-button1").image = "data:image/png;base64,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";

}


/*Initialization Code*/
var prefManager = Components.classes["@mozilla.org/preferences-service;1"]
                    .getService(Components.interfaces.nsIPrefBranch);

// Available methods: getIntPref, getBoolPref, getCharPref
var current = prefManager.getBoolPref( "browser.tabs.loadDivertedInBackground" );

if ( current == false ) {
    document.querySelector("#custombuttons-button1").image = "data:image/png;base64,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";
} else {
    document.querySelector("#custombuttons-button1").image = "data:image/png;base64,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";
}