Test always evaluates the same

Defect 99856 (STATIC_C)
Checker DEADCODE (subcategory redundant_test)
File: /src/third_party/wiredtiger/src/include/btree.i
Function __wt_page_can_evict
/src/third_party/wiredtiger/src/include/btree.i, line: 1212
Condition "mod == NULL", taking false branch. Now the value of "mod" is not "NULL".

    	if (mod == NULL)

/src/third_party/wiredtiger/src/include/btree.i, line: 1266
At condition "mod != NULL", the value of "mod" cannot be "NULL".

    	if (!modified && mod != NULL &&

/src/third_party/wiredtiger/src/include/btree.i, line: 1266
The condition "mod != NULL" must be true.

    	if (!modified && mod != NULL &&