ha_innobase::records_in_range(): Remove a debug assertion

that prohibits an open range (full table).
This assertion catches unnecessary calls to this method, but such calls
are not harming correctness.

storage/innobase/handler/ha_innodb.cc

@@ -7611,7 +7611,6 @@ ha_innobase::records_in_range(
 	mem_heap_t*	heap;
 
 	DBUG_ENTER("records_in_range");
-	DBUG_ASSERT(min_key || max_key);
 
 	ut_a(prebuilt->trx == thd_to_trx(ha_thd()));