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[GunChleoc <fios@xxxxxxxxxxxxxxxxxxx>]

GunChleoc has proposed merging lp:~widelands-dev/widelands/bug-1509301 into lp:widelands.

Requested reviews:
  Widelands Developers (widelands-dev)
Related bugs:
  Bug #1509301 in widelands: "Loading older multiplayer savegame doesn't work"
  https://bugs.launchpad.net/widelands/+bug/1509301

For more details, see:
https://code.launchpad.net/~widelands-dev/widelands/bug-1509301/+merge/275624

Fixed the crash.

What happens here is that the old savegame causes an exception to be thrown. Because of the exception, the ChatOverlay never got assigned a specific ChatProvider, only the generic one. The generic one contains only virtual methods. So, I added a check for this.
-- 
Your team Widelands Developers is requested to review the proposed merge of lp:~widelands-dev/widelands/bug-1509301 into lp:widelands.

=== modified file 'src/wui/chatoverlay.cc'
--- src/wui/chatoverlay.cc	2015-10-04 19:53:09 +0000
+++ src/wui/chatoverlay.cc	2015-10-24 12:20:35 +0000
@@ -21,6 +21,7 @@
 
 #include <memory>
 
+#include "base/macros.h"
 #include "chat/chat.h"
 #include "graphic/font_handler1.h"
 #include "graphic/rendertarget.h"
@@ -67,6 +68,15 @@
 	}
 
 	void recompute();
+
+private:
+	bool has_chat_provider() {
+		if (chat_ == nullptr) return false;
+		// The chat provider might not have been assigned a specific subclass,
+		// e.g. if there was an exception thrown.
+		if (is_a(ChatProvider, chat_)) return false;
+		return true;
+	}
 };
 
 ChatOverlay::ChatOverlay
@@ -116,7 +126,7 @@
 
 	// Parse the chat message list as well as the log message list
 	// and display them in chronological order
-	int32_t chat_idx = chat_ != nullptr ? chat_->get_messages().size() - 1 : -1;
+	int32_t chat_idx = has_chat_provider() ? chat_->get_messages().size() - 1 : -1;
 	int32_t log_idx = log_messages_.empty() ? -1 : log_messages_.size() - 1;
 	std::string richtext;