Timer.clear silently ignores undefined and null (matches clearTimeout)

Author: phoddie

documentation/base/base.md

@@ -1,6 +1,6 @@
 # Base
-Copyright 2017-2020 Moddable Tech, Inc.<BR>
-Revised: October 7, 2020
+Copyright 2017-2022 Moddable Tech, Inc.<BR>
+Revised: March 8, 2022
 
 **Warning**: These notes are preliminary. Omissions and errors are likely. If you encounter problems, please ask for assistance.
 
@@ -98,6 +98,9 @@ Timer.clear(aTimer);
 
 > **Note**: Immediate and one shot timers are automatically cleared after invoking their callback function. There is no need to call `clear` except to cancel the timer before it fires.
 
+> **Note**: If `Timer.clear` is passed a value of `undefined` or `null` for the ID, no exception is generated.
+
+
 ***
 
 ### `Timer.delay(ms)`

modules/base/timer/modTimer.c

@@ -126,8 +126,12 @@ void xs_timer_schedule(xsMachine *the)
 void xs_timer_clear(xsMachine *the)
 {
 	modTimerScript ts;
-	modTimer timer = xsmcGetHostDataValidate(xsArg(0), (void *)&modTimerHooks);
+	modTimer timer;
 
+	if (xsReferenceType != xsmcTypeOf(xsArg(0)))
+		return;
+	
+	timer = xsmcGetHostDataValidate(xsArg(0), (void *)&modTimerHooks);
 	ts = (modTimerScript)modTimerGetRefcon(timer);
 	xsForget(ts->self);
 	ts->callback = NULL;

xs/sources/xsAPI.c

@@ -53,6 +53,10 @@ txKind fxTypeOf(txMachine* the, txSlot* theSlot)
 		return XS_STRING_KIND;
 	if (theSlot->kind == XS_BIGINT_X_KIND)
 		return XS_BIGINT_KIND;
+#ifdef mxHostFunctionPrimitive
+	if (theSlot->kind == XS_HOST_FUNCTION_KIND)
+		return XS_REFERENCE_KIND;
+#endif
 	return theSlot->kind;
 }