Add checks to prilen functions.

Add to prilen funcs:
  - the check that the metric is allocated (avoid memory errors in ParMmg when calling computePrilen)
  - the check that the element array is not empty (avoid infinite edge lengths when mesh->nt = 0, for example after domain deletion)

src/mmg2d/length_2d.c

@@ -140,6 +140,12 @@ int MMG2D_prilen(MMG5_pMesh mesh,MMG5_pSol sol) {
   ibmax = 0;
   nullEdge = 0;
 
+  if ( (!sol) || (!sol->m) ) {
+    /* the functions that computes the edge length cannot be called without an
+     * allocated metric */
+    return 0;
+  }
+
   if ( !mesh->nt ) {
     return 0;
   }

src/mmg3d/quality_3d.c

@@ -241,6 +241,16 @@ int MMG3D_computePrilen( MMG5_pMesh mesh, MMG5_pSol met, double* avlen,
   *amin = *amax = *bmin = *bmax = 0;
   *nullEdge = 0;
 
+  if ( (!met) || (!met->m) ) {
+    /* the functions that computes the edge length cannot be called without an
+     * allocated metric */
+    return 0;
+  }
+
+  if ( !mesh->ne ) {
+    return 0;
+  }
+
   /* Hash all edges in the mesh */
   if ( !MMG5_hashNew(mesh,&hash,mesh->np,7*mesh->np) )  return 0;
 

src/mmgs/quality_s.c

@@ -297,6 +297,16 @@ int MMGS_prilen(MMG5_pMesh mesh, MMG5_pSol met, int metRidTyp) {
   amin = amax = bmin = bmax = 0;
   nullEdge = 0;
 
+  if ( (!met) || (!met->m) ) {
+    /* the functions that computes the edge length cannot be called without an
+     * allocated metric */
+    return 0;
+  }
+
+  if ( !mesh->nt ) {
+    return 0;
+  }
+
   /* Hash all edges in the mesh */
   if ( !MMG5_hashNew(mesh,&hash,mesh->np,7*mesh->np) )  return 0;