timers: fix issue with restart-timer after timer went off.

basis/timers/timers-tests.factor

@@ -64,3 +64,12 @@ threads tools.test tools.time ;
     700 milliseconds sleep dup restart-timer
     700 milliseconds sleep stop-timer 500 milliseconds sleep
 ] unit-test
+
+{ { 2 } } [
+    { 0 }
+    dup '[ 0 _ [ 1 + ] change-nth ] 300 milliseconds f <timer>
+    dup restart-timer
+    700 milliseconds sleep
+    dup restart-timer drop
+    700 milliseconds sleep
+] unit-test

basis/timers/timers.factor

@@ -94,11 +94,10 @@ PRIVATE>
     ] if ;
 
 : restart-timer ( timer -- )
-    t >>restart?
     dup quotation-running?>> [
-        drop
+        t >>restart? drop
     ] [
-        dup thread>> [ nip interrupt ] [ start-timer ] if*
+        dup thread>> [ interrupt ] when* start-timer
     ] if ;
 
 <PRIVATE