Pointer is checked against null but then dereferenced anyway

Defect 98151 (STATIC_C)
Checker FORWARD_NULL (subcategory none)
File: /src/third_party/wiredtiger/src/btree/bt_cursor.c
Function __wt_btcur_range_truncate
/src/third_party/wiredtiger/src/btree/bt_cursor.c, line: 1169
Comparing "start" to null implies that "start" might be null.

    	cbt = (start != NULL) ? start : stop;

File: /src/third_party/wiredtiger/src/btree/bt_cursor.c
Function __wt_btcur_range_truncate
/src/third_party/wiredtiger/src/btree/bt_cursor.c, line: 1169
Comparing "start" to null implies that "start" might be null.

    	cbt = (start != NULL) ? start : stop;

File: /src/third_party/wiredtiger/src/btree/bt_cursor.c
Function __wt_btcur_range_truncate
/src/third_party/wiredtiger/src/btree/bt_cursor.c, line: 1169
Comparing "start" to null implies that "start" might be null.

    	cbt = (start != NULL) ? start : stop;