[SPARK-45430] Fix for FramelessOffsetWindowFunction when IGNORE NULLS…

… and offset > rowCount

### What changes were proposed in this pull request?

This is a fix for the failure when function that utilized `FramelessOffsetWindowFunctionFrame` is used with `ignoreNulls = true` and `offset > rowCount`.

e.g.

```
select x, lead(x, 5) IGNORE NULLS over (order by x) from (select explode(sequence(1, 3)) x)
```

### Why are the changes needed?

Fix existing bug

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

Modify existing unit test to cover this case

### Was this patch authored or co-authored using generative AI tooling?

No

Closes #43236 from vitaliili-db/SPARK-45430.

Authored-by: Vitalii Li <vitalii.li@databricks.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
(cherry picked from commit 32e1e58)
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

sql/core/src/main/scala/org/apache/spark/sql/execution/window/WindowFunctionFrame.scala

@@ -201,7 +201,11 @@ class FrameLessOffsetWindowFunctionFrame(
   override def prepare(rows: ExternalAppendOnlyUnsafeRowArray): Unit = {
     resetStates(rows)
     if (ignoreNulls) {
-      findNextRowWithNonNullInput()
+      if (Math.abs(offset) > rows.length) {
+        fillDefaultValue(EmptyRow)
+      } else {
+        findNextRowWithNonNullInput()
+      }
     } else {
       // drain the first few rows if offset is larger than zero
       while (inputIndex < offset) {

sql/core/src/test/scala/org/apache/spark/sql/DataFrameWindowFunctionsSuite.scala

@@ -819,34 +819,38 @@ class DataFrameWindowFunctionsSuite extends QueryTest
         lead($"value", 1, null, true).over(window),
         lead($"value", 2, null, true).over(window),
         lead($"value", 3, null, true).over(window),
+        // offset > rowCount: SPARK-45430
+        lead($"value", 100, null, true).over(window),
         lead(concat($"value", $"key"), 1, null, true).over(window),
         lag($"value", 1).over(window),
         lag($"value", 2).over(window),
         lag($"value", 0, null, true).over(window),
         lag($"value", 1, null, true).over(window),
         lag($"value", 2, null, true).over(window),
         lag($"value", 3, null, true).over(window),
+        // abs(offset) > rowCount: SPARK-45430
+        lag($"value", -100, null, true).over(window),
         lag(concat($"value", $"key"), 1, null, true).over(window))
         .orderBy($"order"),
       Seq(
-        Row("a", 0, null, "x", null, null, "x", "y", "z", "xa",
-          null, null, null, null, null, null, null),
-        Row("a", 1, "x", null, null, "x", "y", "z", "v", "ya",
-          null, null, "x", null, null, null, null),
-        Row("b", 2, null, null, "y", null, "y", "z", "v", "ya",
-          "x", null, null, "x", null, null, "xa"),
-        Row("c", 3, null, "y", null, null, "y", "z", "v", "ya",
-          null, "x", null, "x", null, null, "xa"),
-        Row("a", 4, "y", null, "z", "y", "z", "v", null, "za",
-          null, null, "y", "x", null, null, "xa"),
-        Row("b", 5, null, "z", "v", null, "z", "v", null, "za",
-          "y", null, null, "y", "x", null, "ya"),
-        Row("a", 6, "z", "v", null, "z", "v", null, null, "va",
-          null, "y", "z", "y", "x", null, "ya"),
-        Row("a", 7, "v", null, null, "v", null, null, null, null,
-          "z", null, "v", "z", "y", "x", "za"),
-        Row("a", 8, null, null, null, null, null, null, null, null,
-          "v", "z", null, "v", "z", "y", "va")))
+        Row("a", 0, null, "x", null, null, "x", "y", "z", null, "xa",
+          null, null, null, null, null, null, null, null),
+        Row("a", 1, "x", null, null, "x", "y", "z", "v", null, "ya",
+          null, null, "x", null, null, null, null, null),
+        Row("b", 2, null, null, "y", null, "y", "z", "v", null, "ya",
+          "x", null, null, "x", null, null, null, "xa"),
+        Row("c", 3, null, "y", null, null, "y", "z", "v", null, "ya",
+          null, "x", null, "x", null, null, null, "xa"),
+        Row("a", 4, "y", null, "z", "y", "z", "v", null, null, "za",
+          null, null, "y", "x", null, null, null, "xa"),
+        Row("b", 5, null, "z", "v", null, "z", "v", null, null, "za",
+          "y", null, null, "y", "x", null, null, "ya"),
+        Row("a", 6, "z", "v", null, "z", "v", null, null, null, "va",
+          null, "y", "z", "y", "x", null, null, "ya"),
+        Row("a", 7, "v", null, null, "v", null, null, null, null, null,
+          "z", null, "v", "z", "y", "x", null, "za"),
+        Row("a", 8, null, null, null, null, null, null, null, null, null,
+          "v", "z", null, "v", "z", "y", null, "va")))
   }
 
   test("lag - Offset expression <offset> must be a literal") {