Cache version.version in MainFrame

Change-Id: I5d2eccb3e1470159f2ee416994c1b1465af8f068
Reviewed-on: http://gerrit.dmdirc.com/418
Tested-by: Gregory Holmes <greboid@dmdirc.com>
Reviewed-by: Chris Smith <chris@dmdirc.com>

src/com/dmdirc/addons/ui_swing/MainFrame.java

     private SwingController controller;
     /** Status bar. */
     private SwingStatusBar statusBar;
+    /** Client Version. */
+    private String version;
 
     /**
      * Creates new form MainFrame.
 
         showVersion = IdentityManager.getGlobalConfig().getOptionBool("ui",
                 "showversion");
+        version = IdentityManager.getGlobalConfig().getOption("version",
+                    "version");
         IdentityManager.getGlobalConfig().addChangeListener("ui", "lookandfeel",
                 this);
         IdentityManager.getGlobalConfig().addChangeListener("ui", "showversion",
     @Override
     public String getTitlePrefix() {
         if (showVersion) {
-            return "DMDirc " + IdentityManager.getGlobalConfig().getOption(
-                    "version", "version");
+            return "DMDirc " + version;
         } else {
             return "DMDirc";
         }