From coverity: URI.getPath may return null

git-svn-id: http://svn.code.sf.net/p/davmail/code/trunk@2261 3d1905a2-6b24-0410-a738-b14d5a86fcbd

src/java/davmail/exchange/dav/DavExchangeSession.java

@@ -1766,6 +1766,9 @@ public class DavExchangeSession extends ExchangeSession {
                 try {
                     URI folderURI = new URI(href, false);
                     folder.folderPath = folderURI.getPath();
+                    if (folder.folderPath == null) {
+                        throw new URIException();
+                    }
                 } catch (URIException e) {
                     throw new DavMailException("EXCEPTION_INVALID_FOLDER_URL", href);
                 }