fixed segmentation fault

Disabled the color field check on downsamplealldata=false

filters/src/voxel_grid.cpp

@@ -258,23 +258,25 @@ pcl::VoxelGrid<pcl::PCLPointCloud2>::applyFilter (PCLPointCloud2 &output)
   Eigen::Vector4f pt  = Eigen::Vector4f::Zero ();
 
   int centroid_size = 4;
-  if (downsample_all_data_)
-    centroid_size = static_cast<int> (input_->fields.size ());
-
   int rgba_index = -1;
 
-  // ---[ RGB special case
-  // if the data contains "rgba" or "rgb", add an extra field for r/g/b in centroid
-  for (int d = 0; d < centroid_size; ++d)
+  if (downsample_all_data_)
   {
-    if (input_->fields[d].name == std::string ("rgba") || input_->fields[d].name == std::string ("rgb"))
+    centroid_size = static_cast<int> (input_->fields.size ());
+
+    // ---[ RGB special case 
+    // if the data contains "rgba" or "rgb", add an extra field for r/g/b in centroid
+    for (int d = 0; d < centroid_size; ++d)
     {
-      rgba_index = d;
-      centroid_size += 4;
-      break;
+      if (input_->fields[d].name == std::string ("rgba") || input_->fields[d].name == std::string ("rgb"))
+      {
+        rgba_index = d;
+        centroid_size += 4;
+        break;
+      }
     }
   }
-
+  
   // If we don't want to process the entire cloud, but rather filter points far away from the viewpoint first...
   if (!filter_field_name_.empty ())
   {