fix: paid amount gets overwritten by get_outstanding_invoices (#20050)

diff --git a/erpnext/accounts/doctype/payment_entry/payment_entry.js b/erpnext/accounts/doctype/payment_entry/payment_entry.js
index adf47ed..2192b7b 100644
--- a/erpnext/accounts/doctype/payment_entry/payment_entry.js
+++ b/erpnext/accounts/doctype/payment_entry/payment_entry.js
@@ -652,14 +652,16 @@
 						(frm.doc.payment_type=="Receive" && frm.doc.party_type=="Student")
 					) {
 						if(total_positive_outstanding > total_negative_outstanding)
-							frm.set_value("paid_amount",
-								total_positive_outstanding - total_negative_outstanding);
+							if (!frm.doc.paid_amount)
+								frm.set_value("paid_amount",
+									total_positive_outstanding - total_negative_outstanding);
 					} else if (
 						total_negative_outstanding &&
 						total_positive_outstanding < total_negative_outstanding
 					) {
-						frm.set_value("received_amount",
-							total_negative_outstanding - total_positive_outstanding);
+						if (!frm.doc.received_amount)
+							frm.set_value("received_amount",
+								total_negative_outstanding - total_positive_outstanding);
 					}
 				}