Updates history previous/next buttons when history finished loading, or if it take too long they will be disabled on the first opened tab.

src/net/java/sip/communicator/impl/gui/main/chat/ChatPanel.java

@@ -1975,6 +1975,8 @@ public void finished()
                 // Add incoming events accumulated while the history was loading
                 // at the end of the chat.
                 addIncomingEvents();
+
+                chatContainer.updateHistoryButtonState(ChatPanel.this);
             }
         };