jscript: Fix Array.reduce when last element doesn't exist.

dlls/jscript/array.c

@@ -1422,8 +1422,10 @@ static HRESULT Array_reduce(script_ctx_t *ctx, jsval_t vthis, WORD flags, unsign
 
     for(k = 0; k < length; k++) {
         hres = jsdisp_get_idx(jsthis, k, &callback_args[1]);
-        if(hres == DISP_E_UNKNOWNNAME)
+        if(hres == DISP_E_UNKNOWNNAME) {
+            hres = S_OK;
             continue;
+        }
         if(FAILED(hres))
             break;
 

dlls/mshtml/tests/es5.js

@@ -1336,6 +1336,9 @@ sync_test("reduce", function() {
     r = [1,2,3].reduce(function(a, value) { return a + value; }, "str");
     ok(r === "str123", "reduce() returned " + r);
 
+    r = [1,2,].reduce(function(a, value) { return a + value; }, "str");
+    ok(r === "str12", "reduce() returned " + r);
+
     array = [1,2,3];
     r = array.reduce(function(a, value, index, src) {
         ok(src === array, "src != array");