fix: don't set finance books if gross_purchase_amount is not set (#37480)

diff --git a/erpnext/assets/doctype/asset/asset.js b/erpnext/assets/doctype/asset/asset.js
index 5395f15..f0e4c82 100644
--- a/erpnext/assets/doctype/asset/asset.js
+++ b/erpnext/assets/doctype/asset/asset.js
@@ -337,7 +337,7 @@
 
 
 	item_code: function(frm) {
-		if(frm.doc.item_code && frm.doc.calculate_depreciation) {
+		if(frm.doc.item_code && frm.doc.calculate_depreciation && frm.doc.gross_purchase_amount) {
 			frm.trigger('set_finance_book');
 		} else {
 			frm.set_value('finance_books', []);
@@ -490,7 +490,7 @@
 
 	calculate_depreciation: function(frm) {
 		frm.toggle_reqd("finance_books", frm.doc.calculate_depreciation);
-		if (frm.doc.item_code && frm.doc.calculate_depreciation ) {
+		if (frm.doc.item_code && frm.doc.calculate_depreciation && frm.doc.gross_purchase_amount) {
 			frm.trigger("set_finance_book");
 		} else {
 			frm.set_value("finance_books", []);