Fix crash when declare timestamps are missing

lib/session.js

@@ -1016,9 +1016,12 @@ function rpcRequest(sessionContext, _declarations, callback) {
           // Enforce max timestamp
           if (d.pathGet > sessionContext.timestamp)
             d.pathGet = sessionContext.timestamp;
-          for (const [k, v] of Object.entries(d.attrGet)) {
-            if (v > sessionContext.timestamp)
-              d.attrGet[k] = sessionContext.timestamp;
+
+          if (d.attrGet) {
+            for (const [k, v] of Object.entries(d.attrGet)) {
+              if (v > sessionContext.timestamp)
+                d.attrGet[k] = sessionContext.timestamp;
+            }
           }
 
           for (const ad of device.getAliasDeclarations(d.path, 1))