usses isset to replace missing keys

This pull request usses ```isset``` to check and replace missing keys, so instead of

```php
$entry['num_hits']=$entry['num_hits']?:$entry['nhits'];
```
it uses

```php
$entry['num_hits']=isset($entry['num_hits'])? $entry['num_hits']:$entry['nhits'];
```

This avoids triggering NOTICEs in PHP.

it also adds the same check/replace login to the IMG=2 graphic (landing page) and avoids several other NOTICEs on that same landing page:

![apcu1](https://cloud.githubusercontent.com/assets/238439/4541950/b8201702-4e1b-11e4-938b-2961011fa633.png)