SDFormat fails to parse <visual> tag hierarchy when new SDF properties are added to <collision> tag hierarchy

**Original report ([archived issue](https://osrf-migration.github.io/sdformat-gh-pages/#!/osrf/sdformat/issues/84)) by faichele (Bitbucket: [Fabian Aichele](https://bitbucket.org/%7B025d8ae6-b2e4-4ddd-862e-10b8ba4d58bc%7D/)).**

The original report had attachments: [surface.sdf](https://osrf-migration.github.io/sdformat-gh-pages/data/repositories/osrf/sdformat/issues/84/attachments/surface.sdf)

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After adding a bunch of new SDF properties to the tag hierarchy (specifically to the tag hierarchy, specification attached), SDFormat fails to parse the tag hierarchy if the tag hierarchy precedes the tag hierarchy. However, if the tag hierarchy is located before the tag hierarchy, both get parsed correctly.

There are no error or warning messages when the added SDF properties are present, the only obvious error is that no visual model is created when creating an instance of a corresponding model in a running Gazebo simulation.

Related to this issue, including output of "gz sdf --print path_to_model/model.sdf": [http://answers.gazebosim.org/question/8098/problem-after-adding-properties-to-sdf-description/](http://answers.gazebosim.org/question/8098/problem-after-adding-properties-to-sdf-description/)