Update VertexTriangleAdjacency.cpp

closes https://github.com/assimp/assimp/issues/2806: calculate corret number of vertices.

code/Common/VertexTriangleAdjacency.cpp

@@ -58,7 +58,7 @@ VertexTriangleAdjacency::VertexTriangleAdjacency(aiFace *pcFaces,
 {
     // compute the number of referenced vertices if it wasn't specified by the caller
     const aiFace* const pcFaceEnd = pcFaces + iNumFaces;
-    if (!iNumVertices)  {
+    if (0 == iNumVertices)  {
         for (aiFace* pcFace = pcFaces; pcFace != pcFaceEnd; ++pcFace)   {
             ai_assert( nullptr != pcFace );
             ai_assert(3 == pcFace->mNumIndices);
@@ -68,7 +68,7 @@ VertexTriangleAdjacency::VertexTriangleAdjacency(aiFace *pcFaces,
         }
     }
 
-    mNumVertices = iNumVertices;
+    mNumVertices = iNumVertices + 1;
 
     unsigned int* pi;