Repacker: refresh sizes before backing up boot

Change-Id: I001295739cb71fdbfc3c3bfe5cc150dc5215867c
diff --git a/twrpRepacker.cpp b/twrpRepacker.cpp
index 2ee5b7d..83ae973 100755
--- a/twrpRepacker.cpp
+++ b/twrpRepacker.cpp
@@ -118,6 +118,7 @@
 		return false;
 	}
 	DataManager::SetProgress(0);
+	PartitionManager.Update_System_Details();
 	TWPartition* part = PartitionManager.Find_Partition_By_Path("/boot");
 	if (part)
 		gui_msg(Msg("unpacking_image=Unpacking {1}...")(part->Get_Display_Name()));