fix: address review comments

- restore mutated SLE after test via addCleanup
- explicit return False in has_difference
- comment the fifo_stock_diff guard for non-queue predecessors

(cherry picked from commit ef5f47fafd)

erpnext/stock/report/stock_ledger_invariant_check/stock_ledger_invariant_check.py

@@ -128,6 +128,7 @@ def add_fifo_fields(sle, prev_sle):
 	sle.fifo_valuation_diff = (
 		sle.valuation_rate - sle.fifo_valuation_rate if sle.fifo_valuation_rate else None
 	)
+	# prev row may not maintain a queue; H and H - F stay blank across the gap
 	if prev_sle and prev_sle.fifo_stock_value is not None:
 		sle.fifo_stock_diff = sle.fifo_stock_value - prev_sle.fifo_stock_value
 		sle.fifo_difference_diff = sle.fifo_stock_diff - sle.stock_value_difference

erpnext/stock/report/stock_ledger_invariant_check/test_stock_ledger_invariant_check.py

@@ -51,6 +51,13 @@ class TestStockLedgerInvariantCheck(ERPNextTestSuite):
 		sle = frappe.get_last_doc(
 			"Stock Ledger Entry", {"item_code": item, "warehouse": WAREHOUSE, "is_cancelled": 0}
 		)
+		self.addCleanup(
+			frappe.db.set_value,
+			"Stock Ledger Entry",
+			sle.name,
+			"qty_after_transaction",
+			sle.qty_after_transaction,
+		)
 		frappe.db.set_value(
 			"Stock Ledger Entry", sle.name, "qty_after_transaction", sle.qty_after_transaction + 5
 		)

erpnext/stock/report/stock_ledger_variance/stock_ledger_variance.py

@@ -297,3 +297,5 @@ def has_difference(row, float_precision, currency_precision, difference_in, valu
 		return True
 	elif difference_in not in ["Qty", "Value", "Valuation"] and (qty_diff or value_diff or valuation_diff):
 		return True
+
+	return False