Fix FloatDomainError when 0 nodes are found

Oxidized would throw:
----
/var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/jobs.rb:36:in `to_i': NaN (FloatDomainError)
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/jobs.rb:36:in `new_count'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/jobs.rb:28:in `duration'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/jobs.rb:16:in `initialize'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/worker.rb:7:in `new'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/worker.rb:7:in `initialize'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/core.rb:21:in `new'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/core.rb:21:in `initialize'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/core.rb:12:in `new'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/core.rb:12:in `new'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/lib/oxidized/cli.rb:9:in `run'
        from /var/lib/gems/2.1.0/gems/oxidized-0.7.2/bin/oxidized:9:in `<top (required)>'
        from /usr/local/bin/oxidized:23:in `load'
        from /usr/local/bin/oxidized:23:in `<main>'
---

When nodes.size == 0, this may happen when you have say one node in router.db which has non-existing model. Actual problem happens in jobs.rb:

@duration = @durations.inject(:+).to_f / @nodes.size
...
@want = ((@nodes.size * @duration) / @interval).to_i

Simplified:

a = 0.0 / 0
b = a.to_i

0 files changed, 0 insertions, 0 deletions