Fix compilation bug when including ViewerCore.h

Former-commit-id: 1345c63ab10aa5428c1de20f15eeda186f95e613

include/igl/viewer/ViewerCore.h

@@ -8,11 +8,11 @@
 #ifndef IGL_VIEWER_VIEWER_CORE_H
 #define IGL_VIEWER_VIEWER_CORE_H
 
+#include <igl/viewer/OpenGL_state.h>
 #ifdef IGL_VIEWER_WITH_NANOGUI
 #include <igl/viewer/TextRenderer.h>
 #endif
 #include <igl/viewer/ViewerData.h>
-#include <igl/viewer/OpenGL_state.h>
 
 #include <igl/igl_inline.h>
 #include <Eigen/Geometry>