[SusiMail] Exception when opening new messages

When opening a new message with SusiMail I get the following error message:

Part ((text/plain)) not shown, because of java.io.IOException: Stream Closed

This is caused by the PersistentMailCache::write method consuming all of the FileBuffer._is without resetting it. The following patch fixes this:

--- a/apps/susimail/src/src/i2p/susi/webmail/PersistentMailCache.java
+++ b/apps/susimail/src/src/i2p/susi/webmail/PersistentMailCache.java
@@ -356,6 +356,7 @@ class PersistentMailCache {
                        GzipFileBuffer gb = new GzipFileBuffer(f);
                        out = gb.getOutputStream();
                        DataHelper.copy(in, out);
+                       rb.readComplete(true);
                        return true;
                } catch (IOException ioe) {
                        _log.error("Error writing: " + f + ": " + ioe);