Adds more tests cases

Author: jcsherin

datafusion/sqllogictest/test_files/window.slt

@@ -4971,6 +4971,26 @@ SELECT LAG(NULL, 1, false) OVER () FROM t1;
 ----
 false
 
+query B
+SELECT LEAD(NULL, 0, true) OVER () FROM t1;
+----
+NULL
+
+query B
+SELECT LAG(NULL, 0, true) OVER () FROM t1;
+----
+NULL
+
+query B
+SELECT LEAD(NULL, 1, true) OVER () FROM t1;
+----
+true
+
+query B
+SELECT LAG(NULL, 1, true) OVER () FROM t1;
+----
+true
+
 statement ok
 insert into t1 values (2);
 
@@ -4986,6 +5006,18 @@ SELECT LAG(NULL, 1, false) OVER () FROM t1;
 false
 NULL
 
+query B
+SELECT LEAD(NULL, 1, true) OVER () FROM t1;
+----
+NULL
+true
+
+query B
+SELECT LAG(NULL, 1, true) OVER () FROM t1;
+----
+true
+NULL
+
 statement ok
 DROP TABLE t1;