Mesh: [skip ci] Fix coverity warning

Coverity warnings fixed:

CID 316517 (#1 of 1): Uninitialized scalar variable (UNINIT)
13. uninit_use_in_call: Using uninitialized value t. Field t.err is uninitialized when calling push_back

CID 316519 (#1 of 1): Uninitialized scalar variable (UNINIT)
3. uninit_use_in_call: Using uninitialized value v. Field v.tstart is uninitialized when calling push_back

CID 316547 (#1 of 1): Uninitialized scalar variable (UNINIT)
13. uninit_use_in_call: Using uninitialized value t. Field t.err is uninitialized when calling push_back

CID 316556 (#1 of 1): Uninitialized scalar variable (UNINIT)
3. uninit_use_in_call: Using uninitialized value v. Field v.tstart is uninitialized when calling push_back

src/Mod/Mesh/App/Core/Decimation.cpp

@@ -52,13 +52,16 @@ void MeshSimplify::simplify(float tolerance, float reduction)
     const MeshPointArray& points = myKernel.GetPoints();
     for (std::size_t i = 0; i < points.size(); i++) {
         Simplify::Vertex v;
+        v.tstart = 0;
         v.p = points[i];
         alg.vertices.push_back(v);
     }
 
     const MeshFacetArray& facets = myKernel.GetFacets();
     for (std::size_t i = 0; i < facets.size(); i++) {
         Simplify::Triangle t;
+        for (int j = 0; j < 4; j++)
+            t.err[j] = 0.0;
         for (int j = 0; j < 3; j++)
             t.v[j] = facets[i]._aulPoints[j];
         alg.triangles.push_back(t);
@@ -103,13 +106,16 @@ void MeshSimplify::simplify(int targetSize)
     const MeshPointArray& points = myKernel.GetPoints();
     for (std::size_t i = 0; i < points.size(); i++) {
         Simplify::Vertex v;
+        v.tstart = 0;
         v.p = points[i];
         alg.vertices.push_back(v);
     }
 
     const MeshFacetArray& facets = myKernel.GetFacets();
     for (std::size_t i = 0; i < facets.size(); i++) {
         Simplify::Triangle t;
+        for (int j = 0; j < 4; j++)
+            t.err[j] = 0.0;
         for (int j = 0; j < 3; j++)
             t.v[j] = facets[i]._aulPoints[j];
         alg.triangles.push_back(t);