Pointer is checked against null but then dereferenced anyway

Defect 72910 (STATIC_C)
Checker FORWARD_NULL (subcategory none)
File: /src/mongo/db/cloner.cpp
Function mongo::Cloner::Fun::operator ()(mongo::DBClientCursorBatchIterator &)
/src/mongo/db/cloner.cpp, line: 138
Comparing "collection" to null implies that "collection" might be null.

            if (!collection) {