Werk #4339: fixed AtrributeError in oracle sessions ruleset

Component	Checks & agents
Title	fixed AtrributeError in oracle sessions ruleset
Date	Feb 7, 2017
Level	Trivial Change
Class	Bug Fix
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	1.4.0b1 Checkmk Community, Checkmk Pro, Checkmk Ultimate MT

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