fix: Get invoice details only if invoice is selected
diff --git a/erpnext/accounts/doctype/c_form/c_form.js b/erpnext/accounts/doctype/c_form/c_form.js
index 3d0fc0a..846408f 100644
--- a/erpnext/accounts/doctype/c_form/c_form.js
+++ b/erpnext/accounts/doctype/c_form/c_form.js
@@ -32,10 +32,12 @@
 	invoice_no(frm, cdt, cdn) {
 		let d = frappe.get_doc(cdt, cdn);
 
-		frm.call('get_invoice_details', {
-			invoice_no: d.invoice_no
-		}).then(r => {
-			frappe.model.set_value(cdt, cdn, r.message);
-		});
+		if (d.invoice_no) {
+			frm.call('get_invoice_details', {
+				invoice_no: d.invoice_no
+			}).then(r => {
+				frappe.model.set_value(cdt, cdn, r.message);
+			});
+		}
 	}
 });