only use structure opt for mpid

emmet-core/emmet/core/vasp/material.py

@@ -55,10 +55,6 @@ def from_tasks(
         if len(task_group) == 0:
             raise Exception("Must have more than one task in the group.")
 
-        # Material ID
-        possible_mat_ids = [task.task_id for task in task_group]
-        material_id = min(possible_mat_ids)
-
         # Metadata
         last_updated = max(task.last_updated for task in task_group)
         created_at = min(task.completed_at for task in task_group)
@@ -82,6 +78,9 @@ def from_tasks(
             else structure_optimizations
         )
 
+        # Material ID
+        possible_mat_ids = [task.task_id for task in structure_optimizations]
+        material_id = min(possible_mat_ids)
         def _structure_eval(task: TaskDocument):
             """
             Helper function to order structures optimziation and statics calcs by