Catch NullPointerException to avoid crash due to unsupported async disconnects on Android L (which uses an outdated okhttp version)

Author: arthurpalves

library/src/main/java/com/danikula/videocache/HttpUrlSource.java

@@ -76,7 +76,13 @@ private int readSourceAvailableBytes(HttpURLConnection connection, int offset, i
     @Override
     public void close() throws ProxyCacheException {
         if (connection != null) {
-            connection.disconnect();
+            try {
+                connection.disconnect();
+            } catch (NullPointerException e) {
+                // https://github.com/danikula/AndroidVideoCache/issues/32
+                // https://github.com/danikula/AndroidVideoCache/issues/29
+                throw new ProxyCacheException("Error disconnecting HttpUrlConnection", e);
+            }
         }
     }