ZP-1242 Check for cpid directly instead of getting charset.

Released under the Affero GNU General Public License (AGPL) version 3.

src/backend/kopano/mapiprovider.php

@@ -2476,7 +2476,7 @@ class MAPIProvider {
             }
             elseif (isset($message->internetcpid) && $bpReturnType == SYNC_BODYPREFERENCE_HTML) {
                 // if PR_HTML is UTF-8 we can stream it directly, else we have to convert to UTF-8 & wrap it
-                if (Utils::GetCodepageCharset($message->internetcpid) == "utf-8") {
+                if ($message->internetcpid == INTERNET_CPID_UTF8) {
                     $message->asbody->data = MAPIStreamWrapper::Open($stream, $truncateHtmlSafe);
                 }
                 else {