trim url when preparing it

src/de/danoeh/antennapod/util/URLChecker.java

@@ -23,7 +23,7 @@ public final class URLChecker {
      * */
     public static String prepareURL(String url) {
         StringBuilder builder = new StringBuilder();
-
+        url = url.trim();
         if (!url.startsWith("http")) {
             builder.append("http://");
             if (AppConfig.DEBUG) Log.d(TAG, "Missing http; appending");