fix: Call popup avatar

Avoid getting session users image if customer doc has no image
diff --git a/erpnext/public/js/call_popup/call_popup.js b/erpnext/public/js/call_popup/call_popup.js
index 91dfe80..89657a1 100644
--- a/erpnext/public/js/call_popup/call_popup.js
+++ b/erpnext/public/js/call_popup/call_popup.js
@@ -109,7 +109,7 @@
 		});
 		wrapper.append(`
 			<div class="caller-info flex">
-				${frappe.avatar(null, 'avatar-xl', contact.name, contact.image)}
+				${frappe.avatar(null, 'avatar-xl', contact.name, contact.image || '')}
 				<div>
 					<h5>${contact_name}</h5>
 					<div>${contact.mobile_no || ''}</div>