Checkmk Werk 14565: <tt>inv_if</tt>: Fix crash on innovaphone IP811

ID: 14565 Title: <tt>inv_if</tt>: Fix crash on innovaphone IP811 Component: Checks & agents Level: 1 Class: Bug fix Version: 2.2.0i1 Previously, the inventory plugin <tt>inv_if</tt> would crash while inventorizing interfaces on a innovaphone IP811 with the message C+: Parsing of section inv_if failed C-: This could potentially happen on other devices, if they report 'NULL' to indicate missing values. With this werk, interfaces with this kind of missing information are omitted.