Fix falling tests and pending event handler behaviour

Fix a bug that machine was processing pending event if PendingEventHandler was set to no-throwing implementation.

Author: nsk90

kstatemachine/src/main/kotlin/ru/nsk/kstatemachine/StateMachineImpl.kt

@@ -106,9 +106,14 @@ internal class StateMachineImpl(name: String?, childMode: ChildMode, override va
         check(!isDestroyed) { "$this is already destroyed" }
         check(isRunning) { "$this is not started, call start() first" }
 
+        if (isProcessingEvent) {
+            pendingEventHandler.onPendingEvent(event, argument)
+            // pending event cannot be processed while previous event is still processing
+            // even if PendingEventHandler does not throw
+            return
+        }
+
         runCheckingExceptions {
-            if (isProcessingEvent)
-                pendingEventHandler.onPendingEvent(event, argument)
             isProcessingEvent = true
 
             try {

kstatemachine/src/test/kotlin/ru/nsk/kstatemachine/ListenerExceptionHandlerTest.kt

@@ -37,14 +37,11 @@ class ListenerExceptionHandlerTest : StringSpec({
 
         val machine = createStateMachine(start = false) {
             onStarted { callbacks.onStarted(this) }
-
-            onEntry {
-                callbacks.listen(this)
-                error("test exception")
-            }
+            callbacks.listen(this)
+            onEntry { error("test exception") }
 
             state1 = initialState {
-                onEntry { callbacks.listen(this) }
+                callbacks.listen(this)
             }
         }
         shouldThrow<IllegalStateException> { machine.start() }

kstatemachine/src/test/kotlin/ru/nsk/kstatemachine/StateMachineTest.kt

@@ -167,8 +167,10 @@ class StateMachineTest : StringSpec({
         shouldThrowUnit<IllegalStateException> { machine.setInitialState(first) }
     }
 
-    "pending event handler" {
+    "throwing PendingEventHandler does not destroy machine" {
         val machine = createStateMachine {
+            logger = StateMachine.Logger { println(it) }
+
             val second = state("second")
             initialState("first") {
                 transition<SwitchEvent> {
@@ -184,8 +186,8 @@ class StateMachineTest : StringSpec({
             }
         }
 
-        shouldThrow<IllegalStateException> { machine.processEvent(SwitchEvent) }
-        machine.isDestroyed shouldBe true
+        machine.processEvent(SwitchEvent)
+        machine.isDestroyed shouldBe false
     }
 
     "process event before started" {