[Fix] If two po consolidated in one purchase invoice, Total Net Weight not get summed (#14230)

diff --git a/erpnext/controllers/taxes_and_totals.py b/erpnext/controllers/taxes_and_totals.py
index a4d9dae..b44f597 100644
--- a/erpnext/controllers/taxes_and_totals.py
+++ b/erpnext/controllers/taxes_and_totals.py
@@ -38,6 +38,7 @@
 		self.manipulate_grand_total_for_inclusive_tax()
 		self.calculate_totals()
 		self._cleanup()
+		self.calculate_total_net_weight()
 
 	def validate_conversion_rate(self):
 		# validate conversion rate
@@ -328,6 +329,13 @@
 
 		self.set_rounded_total()
 
+	def calculate_total_net_weight(self):
+		if self.doc.meta.get_field('total_net_weight'):
+			self.doc.total_net_weight = 0.0
+			for d in self.doc.items:
+				if d.total_weight:
+					self.doc.total_net_weight += d.total_weight
+
 	def set_rounded_total(self):
 		if self.doc.meta.get_field("rounded_total"):
 			if self.doc.is_rounded_total_disabled():