Fix for issue #2872. In case of missing values (e.g., zeros when using a logarithmic scale), draw_path_collection may get offsets containing NaN's. In that case, using CGContextTranslateCTM once with translation and once with -translation will not restore the original CTM. This bugfix adds a check for NaN/inf.
Merge pull request #2875 from mdehoon/issue2872bugfix

Fix for issue #2872. Skip NaN's in draw_path_collection.