fix for #105659. fix js warnings when there isn't a mapiregistry service.

r=srilatha, sr=mscott

mailnews/base/prefs/resources/content/accountUtils.js

@@ -81,13 +81,20 @@ function getInvalidAccounts(accounts)
 // This will bring up the dialog only once per session and only if we
 // are not the default mail client.
 function showMailIntegrationDialog() {
-      try {
-        var mapiRegistry = Components.classes[ "@mozilla.org/mapiregistry;1" ].
-                       getService( Components.interfaces.nsIMapiRegistry );
+    var mapiRegistry;
+    try {
+        var mapiRegistryProgID = "@mozilla.org/mapiregistry;1" 
+        if (mapiRegistryProgID in Components.classes) {
+          mapiRegistry = Components.classes[mapiRegistryProgID].getService(Components.interfaces.nsIMapiRegistry);
+        }
+        else {
+          mapiRegistry = null;
+        }
     }
     catch (ex) { 
         mapiRegistry = null;
     }
+
     // showDialog is TRUE only if we did not bring up this dialog already
     // and we are not the default mail client
     var prefLocked = false;