bugfix: principal_curvature returns boolean instead of segfault

Former-commit-id: 8f6a4c4c07f9e180d0214fe418413948c6c22c10

include/igl/principal_curvature.cpp

@@ -780,7 +780,7 @@ template <
   typename DerivedPD2,
   typename DerivedPV1,
   typename DerivedPV2>
-IGL_INLINE void igl::principal_curvature(
+IGL_INLINE bool igl::principal_curvature(
   const Eigen::PlainObjectBase<DerivedV>& V,
   const Eigen::PlainObjectBase<DerivedF>& F,
   Eigen::PlainObjectBase<DerivedPD1>& PD1,
@@ -817,6 +817,8 @@ IGL_INLINE void igl::principal_curvature(
 
   // Compute
   cc.computeCurvature();
+  if (!cc.curvatureComputed)
+    return false;
 
   // Copy it back
   for (unsigned i=0; i<V.rows(); ++i)
@@ -843,6 +845,8 @@ IGL_INLINE void igl::principal_curvature(
     }
   }
 
+  return true;
+
 }
 
 #ifdef IGL_STATIC_LIBRARY

include/igl/principal_curvature.h

@@ -49,7 +49,7 @@ template <
   typename DerivedPD2, 
   typename DerivedPV1, 
   typename DerivedPV2>
-IGL_INLINE void principal_curvature(
+IGL_INLINE bool principal_curvature(
   const Eigen::PlainObjectBase<DerivedV>& V,
   const Eigen::PlainObjectBase<DerivedF>& F,
   Eigen::PlainObjectBase<DerivedPD1>& PD1,