rs: add error dialog for js5io and crash errors

runelite-client/src/main/java/net/runelite/client/rs/RSAppletStub.java

@@ -140,10 +140,31 @@ public void showDocument(URL url)
 								.addButton("Game Status", () -> LinkBrowser.browse("https://secure.runescape.com/m=news/game-status-information-centre?oldschool=1"))
 								.open());
 					}
+					else if (code.equals("error_game_js5io"))
+					{
+						SwingUtilities.invokeLater(() ->
+							new FatalErrorDialog("OldSchool RuneScape is unable to retrieve updates from its update server. " +
+								"This is likely due to a firewall blocking the RuneScape server. Try disabling your firewall, or use " +
+								"a different network.")
+								.setTitle("RuneLite", "Unable to connect to update server")
+								.addHelpButtons()
+								.open());
+					}
+					else if (code.equals("error_game_crash"))
+					{
+						SwingUtilities.invokeLater(() ->
+							new FatalErrorDialog("OldSchool RuneScape has crashed. Crashes are most commonly caused by plugin hub plugins, " +
+								"but can also be caused by RuneLite or Jagex client bugs. If you receive this message commonly, try playing in " +
+								"safe mode to eliminate the potential of plugins causing the crash. The client log file will contain additional " +
+								"information about the crash.")
+								.setTitle("RuneLite", "OldSchool RuneScape has crashed")
+								.addHelpButtons()
+								.open());
+					}
 					else
 					{
 						SwingUtilities.invokeLater(() ->
-							new FatalErrorDialog("OldSchool RuneScape has crashed with the message: " + code + "")
+							new FatalErrorDialog("OldSchool RuneScape has crashed with the message: " + code)
 								.setTitle("RuneLite", "OldSchool RuneScape has crashed")
 								.addHelpButtons()
 								.open());