lib/nbt: Fix not actually returning from Compound::setElementPointerAt in the do nothing case

src/lib/nbt.cpp

@@ -992,6 +992,7 @@ namespace NBT {
                 if (position == this->tags.size() && pointer->getTagType() == TagType::END) {
                     delete pointer;
                     // do nothing, already have one of those
+                    return ErrorOrVoid();
                 } else {
                     delete pointer;
                     // End tags may only go at the end and