fix crash in rqt_dep

[vrabaud]

This fixes an old bad search/replace: set_color was renamed for this qt_dotgraph objects, but on that line it's a normal Pydot object.

[tfoote]

+1 just ran into this too. rqt_dep is not useable.without htis.

[ablasdel]

+1 this fix makes it work for me too.

[dirk-thomas]

Regression of #40.

Just by reading the diff I would assume that the following two changes are also wrong:

• https://github.com/ros-visualization/qt_gui_core/pull/40/files#diff-8e5744e247c143eef18fa52003ec7dd9R131
• https://github.com/ros-visualization/qt_gui_core/pull/40/files#diff-8e5744e247c143eef18fa52003ec7dd9R133

Can someone please confirm this by running the code in question? And update this PR if applicable?

[tfoote]

I cannot test that code path easily as it's only for dry stacks that clusters are generated. And on my saucy machine I don' thave convenient dry stacks. But from reading the code those lines should be changed too. They won't cause crashes due to the if clause, but I would suggest changing those lines too.

I've tested with and without the extra two lines changes and experienced no crashes or errors (wet only)