Build fix; apparently some errors don't include a message, which was causing us to return undefined.

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@1266 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/user/src/com/google/gwt/http/client/XMLHTTPRequest.java b/user/src/com/google/gwt/http/client/XMLHTTPRequest.java
index 53898e7..59f370c 100644
--- a/user/src/com/google/gwt/http/client/XMLHTTPRequest.java
+++ b/user/src/com/google/gwt/http/client/XMLHTTPRequest.java
@@ -176,7 +176,7 @@
       xmlHttpRequest.open(httpMethod, url, async);
       return null;
     } catch (e) {
-      return e.message;
+      return e.message || e.toString();
     }
   }-*/;
 
@@ -198,7 +198,7 @@
       xmlHttpRequest.open(httpMethod, url, async, user);
       return null;
     } catch (e) {
-      return e.message;
+      return e.message || e.toString();
     }
   }-*/;
 
@@ -221,7 +221,7 @@
       xmlHttpRequest.open(httpMethod, url, async, user, password);
       return null;
     } catch (e) {
-      return e.message;
+      return e.message || e.toString();
     }
   }-*/;
 
@@ -242,7 +242,7 @@
       return null;
     } catch (e) {
       xmlHttpRequest.onreadystatechange = @com.google.gwt.user.client.impl.HTTPRequestImpl::nullFunc;
-      return e.message;
+      return e.message || e.toString();
     }
   }-*/;
 
@@ -252,7 +252,7 @@
       xmlHttpRequest.setRequestHeader(header, value);
       return null;
     } catch (e) {
-      return e.message;
+      return e.message || e.toString();
     }
   }-*/;