fixed exception handling

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

core/src/main/java/de/srsoftware/umbrella/core/Util.java

@@ -163,6 +163,8 @@ public class Util {
 				is.close();
 				throw new UmbrellaException(500, bos.toString(UTF_8));
 			}
+		} catch (UmbrellaException e){
+			throw e;
 		} catch (Exception e) {
 			LOG.log(WARNING,"Request to {0} failed: {1}",target,e.getMessage());
 			throw new UmbrellaException(500,"Request to {0} failed!",target).causedBy(e);