* In commit 86b2cd70f9 an extra argument
was added to the `add_large_plant()` function in order to handle silk
touch. For some reason, the callers for "double_grass" and
"double_fern" were updated with two new arguments. Because of this,
silk touch likely never worked on these nodes. This commit removes
the unused `nil` argument from both callers.
* This commit fixes#2155.