tdf#146703 Fix URL encoding when querying extensions

so that extension information files are properly downloaded such as:
https://extensions.libreoffice.org/api/v0/Color Palette.json

Change-Id: Ifb2688b1f09d91277b7d5fe065b0d0f8533310b0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/128306
Tested-by: Jenkins
Reviewed-by: Thorsten Behrens <thorsten.behrens@allotropia.de>
(cherry picked from commit 348e0651cc5add15ac03b11dde08057cf33f9b16)
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/128246
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
diff --git a/cui/source/dialogs/AdditionsDialog.cxx b/cui/source/dialogs/AdditionsDialog.cxx
index ec17374..aa36bf4 100644
--- a/cui/source/dialogs/AdditionsDialog.cxx
+++ b/cui/source/dialogs/AdditionsDialog.cxx
@@ -80,7 +80,9 @@ std::string ucbGet(const OUString& rURL)
{
    try
    {
        auto const s = utl::UcbStreamHelper::CreateStream(rURL, StreamMode::STD_READ);
        OUString sEncodedUrl = INetURLObject::encode(rURL, INetURLObject::PART_FPATH,
                                                     INetURLObject::EncodeMechanism::All);
        auto const s = utl::UcbStreamHelper::CreateStream(sEncodedUrl, StreamMode::STD_READ);
        if (!s)
        {
            SAL_WARN("cui.dialogs", "CreateStream <" << rURL << "> failed");