CHANGE: allow unset none to be a no-op instead of throwing an error

implements: Oldes/Rebol-wishes#28

src/boot/natives.reb

@@ -594,7 +594,7 @@ type?: native [
 
 unset: native [
 	{Unsets the value of a word (in its current context.)}
-	word [word! block!] {Word or block of words}
+	word [word! block! none!] {Word or block of words}
 ]
 
 utf?: native [

src/core/n-data.c

@@ -686,6 +686,9 @@ static int Check_Char_Range(REBVAL *val, REBINT limit)
 			value = Get_Var(word);
 			SET_UNSET(value);
 		} else Trap1(RE_NOT_DEFINED, word);
+	} else if (IS_NONE(word)) {
+		// https://github.com/Oldes/Rebol-wishes/issues/28
+		return R_NONE;
 	} else {
 		for (word = VAL_BLK_DATA(word); NOT_END(word); word++) {
 			if (IS_WORD(word)) {

src/tests/units/object-test.r3

@@ -203,6 +203,7 @@ Rebol [
 		--assert not same? a b
 ===end-group===
 
+
 ===start-group=== "Object actions"
 	--test-- "empty?"
 	;@@ https://github.com/Oldes/Rebol-issues/issues/1669
@@ -215,6 +216,23 @@ Rebol [
 ===end-group===
 
 
+===start-group=== "UNSET in object"
+	--test-- "unset ctx"
+	ctx: context [a: 1 b: 2 c: 3]
+	--assert unset? unset in ctx 'a
+	--assert unset? unset bind [b c] ctx
+	--assert all [
+		unset? :ctx/a
+		unset? :ctx/b
+		unset? :ctx/c
+	]
+	;@@ https://github.com/Oldes/Rebol-wishes/issues/28
+	--assert none? unset in ctx 'd
+
+
+===end-group===
+
+
 ===start-group=== "APPEND on OBJECT"
 	;@@ https://github.com/Oldes/Rebol-issues/issues/708
 	--test-- "issue-708"