Corrected detection of hexahedral meshes in case no cells are defined.

git-svn-id: http://www.openvolumemesh.org/svnrepo/OpenVolumeMesh/trunk@156 66977474-1d4b-4f09-8fe9-267525286df2

src/OpenVolumeMesh/FileManager/FileManager.cc

@@ -166,6 +166,7 @@ bool FileManager::isHexahedralMesh(const std::string& _filename) const {
 
   // Read in number of cells
   iff >> n;
+  if(n == 0) return false;
   unsigned int v = 0;
   char tmp[256];
   for (unsigned int i = 0; i < n; ++i) {