We assign hdr=NULL; in __page_merge_base_internal_deltas but we overwrite it before it's used.

An assigned value that is never used may represent unnecessary computation, an incorrect algorithm, or possibly the need for cleanup or refactoring. A value assigned to a variable is never used.
/src/btree/bt_page.c:518: UNUSED_VALUE 184146 Overwriting previous write to "hdr" with value from "(WT_PAGE_HEADER *)new_image->data".
/src/btree/bt_page.c:349: UNUSED_VALUE 184146 Assigning value "NULL" to "hdr" here, but that stored value is overwritten before it can be used.