Apply custom theme to a site collection using sharepoint hosted app

Hi,

I am trying to apply a custom theme to a site in a sharepoint hosted app. The code is as follows:

$(document).ready(function () {
    hostweburl =decodeURIComponent(getQueryStringParameter("SPHostUrl"));
    appweburl =decodeURIComponent(getQueryStringParameter("SPAppWebUrl"));
    var scriptbase = hostweburl + "/_layouts/15/";
    $.getScript(scriptbase + "SP.RequestExecutor.js");
});

//This is called on a button click

function ApplyTheme() {
  
    var executor = new SP.RequestExecutor(appweburl);
    executor.executeAsync(
                {
                  
                    url: "http://sharepointsite/_api/web/applytheme",
                    method: "POST",
                    data: "{'colorPaletteUrl':'/_catalogs/theme/15/palette005.spcolor','fontSchemeUrl':'/_catalogs/theme/15/fontscheme007.spfont','backgroundImageUrl':'','shareGenerated':false}",
                    headers: {
                        "Accept": "application/json; odata=verbose",
                        "content-type": "application/json;odata=verbose",
                        "X-RequestDigest": $("#__REQUESTDIGEST").val(),

                    },
                    success: successHandler,
                    error: errorHandler
                }
            );

    function successHandler() {alert("Updated"):

    function errorHandler(data, errorCode, errorMessage) {alert(errorMessage)}

}

However I am receving the error "JavaScript runtime error: Invalid field or parameter requestInfo.url.". I did tried to use the encodeURIComponent on my URL but that didnt helped me.