Mantis#2048. Thank you kindly, HomerHorwitz for a patch that:

The attached patch (against r6075) fixes it for grid-mode. If the 
home-region isn't available, the stored regionHandle will be used 
to compute the region-coordinates of the home. This will be wrong 
if the home-region has moved, of course, but without the region 
being online we can't request the RegionInfo of it for finding out. 
Doing that (before the patch) and accessing the (null) RegionInfo 
led to a NullReferenceException, which prevented logging in to the 
last location.

1 files changed, 28 insertions, 8 deletions

diff --git a/OpenSim/Grid/UserServer/UserLoginService.cs b/OpenSim/Grid/UserServer/UserLoginService.cs
index 198f95c..1f84346 100644
--- a/OpenSim/Grid/UserServer/UserLoginService.cs
+++ b/OpenSim/Grid/UserServer/UserLoginService.cs
@@ -215,13 +215,33 @@ namespace OpenSim.Grid.UserServer
                 // Customise the response
                 //CFK: This is redundant and the next message should always appear.
                 //CFK: m_log.Info("[LOGIN]: Home Location");
-                response.Home =
-                    string.Format(
-                        "{{'region_handle':[r{0},r{1}], 'position':[r{2},r{3},r{4}], 'look_at':[r{5},r{6},r{7}]}}",
-                        (HomeInfo.regionLocX*Constants.RegionSize),
-                        (HomeInfo.regionLocY*Constants.RegionSize),
-                        theUser.HomeLocation.X, theUser.HomeLocation.Y, theUser.HomeLocation.Z,
-                        theUser.HomeLookAt.X, theUser.HomeLookAt.Y, theUser.HomeLookAt.Z);
+                if (HomeInfo != null)
+                {
+                    response.Home =
+                        string.Format(
+                            "{{'region_handle':[r{0},r{1}], 'position':[r{2},r{3},r{4}], 'look_at':[r{5},r{6},r{7}]}}",
+                            (HomeInfo.regionLocX*Constants.RegionSize),
+                            (HomeInfo.regionLocY*Constants.RegionSize),
+                            theUser.HomeLocation.X, theUser.HomeLocation.Y, theUser.HomeLocation.Z,
+                            theUser.HomeLookAt.X, theUser.HomeLookAt.Y, theUser.HomeLookAt.Z);
+                }
+                else
+                {
+                    // Emergency mode: Home-region isn't available, so we can't request the region info.
+                    // Use the stored home regionHandle instead.
+                    // NOTE: If the home-region moves, this will be wrong until the users update their user-profile again
+                    ulong regionX = theUser.HomeRegion >> 32;
+                    ulong regionY = theUser.HomeRegion & 0xffffffff;
+                    response.Home =
+                        string.Format(
+                            "{{'region_handle':[r{0},r{1}], 'position':[r{2},r{3},r{4}], 'look_at':[r{5},r{6},r{7}]}}",
+                            regionX, regionY,
+                            theUser.HomeLocation.X, theUser.HomeLocation.Y, theUser.HomeLocation.Z,
+                            theUser.HomeLookAt.X, theUser.HomeLookAt.Y, theUser.HomeLookAt.Z);
+                    m_log.InfoFormat("[LOGIN] Home region of user {0} {1} is not available; using computed region position {2} {3}",
+                                     theUser.FirstName, theUser.SurName,
+                                     regionX, regionY);
+                }
 
                 // Destination
                 //CFK: The "Notifying" message always seems to appear, so subsume the data from this message into
@@ -507,4 +527,4 @@ namespace OpenSim.Grid.UserServer
                     userID));
         }
     }
-}
\ No newline at end of file
+}