throw invalid viewType exception

src/main/java/eu/siacs/conversations/entities/Conversation.java

@@ -2666,6 +2666,10 @@ public class Conversation extends AbstractEntity implements Blockable, Comparabl
                         }
                     }
 
+                    if (viewType == -1) {
+                        throw new RuntimeException("Invalid field " + responseElement.getName() + " " + formType + " " + fieldType + " " + el.getName() + " " + el);
+                    }
+
                     return new Field(eu.siacs.conversations.xmpp.forms.Field.parse(el), viewType);
                 }
 
@@ -2689,10 +2693,22 @@ public class Conversation extends AbstractEntity implements Blockable, Comparabl
                             return field;
                         }
                     }
+
+                    if (viewType == -1) {
+                        throw new RuntimeException("Invalid element " + el.getName() + " " + el.getNamespace() + " " + el);
+                    }
                 } else if (response != null) {
                     viewType = TYPE_ERROR;
                 }
 
+                if (viewType == -1) {
+                    if (responseElement == null) {
+                        throw new RuntimeException("Invalid element - nullable response");
+                    } else {
+                        throw new RuntimeException("Invalid element, type " + response.getType());
+                    }
+                }
+
                 Item item = new Item(el, viewType);
                 items.put(pos, item);
                 return item;