fix: skip empty dimension values in exchange gain loss

(cherry picked from commit 7df9d95)

Author: ravibharathi656

erpnext/accounts/utils.py

@@ -454,7 +454,8 @@ def _build_dimensions_dict_for_exc_gain_loss(
 	dimensions_dict = frappe._dict()
 	if entry and active_dimensions:
 		for dim in active_dimensions:
-			dimensions_dict[dim.fieldname] = entry.get(dim.fieldname)
+			if entry_dimension := entry.get(dim.fieldname):
+				dimensions_dict[dim.fieldname] = entry_dimension
 	return dimensions_dict