enlage preview from attachment staging area, fixes #202

src/org/thoughtcrime/securesms/MediaPreviewActivity.java

@@ -220,6 +220,7 @@ public class MediaPreviewActivity extends PassphraseRequiredActionBarActivity
       Log.w(TAG, "Unsupported media type sent to MediaPreviewActivity, finishing.");
       Toast.makeText(getApplicationContext(), R.string.error, Toast.LENGTH_LONG).show();
       finish();
+      return;
     }
 
     Log.w(TAG, "Loading Part URI: " + initialMedia);

src/org/thoughtcrime/securesms/mms/AttachmentManager.java

@@ -462,6 +462,7 @@ public class AttachmentManager {
       intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
       intent.putExtra(MediaPreviewActivity.DC_MSG_ID, slide.getDcMsgId());
       intent.putExtra(MediaPreviewActivity.OUTGOING_EXTRA, true);
+      intent.setDataAndType(slide.getUri(), slide.getContentType());
 
       context.startActivity(intent);
     }