timer: Dispatch the whole timer in the main block.

Timer.st

@@ -125,7 +125,7 @@ bit difficult to do this race free.'>
 
             (Delay forSeconds: 1) wait.
             now := DateTime now.
-            self fireTimers: now.
+            OsmoDispatcher dispatchBlock: [self fireTimers: now].
         ]
     ]
 
@@ -143,7 +143,11 @@ bit difficult to do this race free.'>
         copy do: [:each |
             each timeout > now ifTrue: [^true].
             sem critical: [queue remove: each].
-            OsmoDispatcher dispatchBlock: [each fire].
+            [
+                each fire
+            ] on: Error do: [:e |
+                e logException: 'Execution of timer failed: %1' % {e tag} area: #timer.
+            ].
         ].
     ]
 ]