Merge to M45: Fix JS_GetArrayElement to not return an empty handle on success

BUG=chromium:528376
TBR=jochen@chromium.org

Review URL: https://codereview.chromium.org/1337433002 .

(cherry picked from commit 0d0935d3d6603dd7d851b1d5828635230f4c43ca)

Review URL: https://codereview.chromium.org/1364833002 .
diff --git a/fpdfsdk/src/jsapi/fxjs_v8.cpp b/fpdfsdk/src/jsapi/fxjs_v8.cpp
index 7adfc26..af00003 100644
--- a/fpdfsdk/src/jsapi/fxjs_v8.cpp
+++ b/fpdfsdk/src/jsapi/fxjs_v8.cpp
@@ -635,7 +635,7 @@
 {
 	if(pArray.IsEmpty()) return v8::Local<v8::Value>();
         v8::Local<v8::Value> val;
-	if (pArray->Get(pJSRuntime->GetCurrentContext(), index).ToLocal(&val)) return v8::Local<v8::Value>();
+	if (!pArray->Get(pJSRuntime->GetCurrentContext(), index).ToLocal(&val)) return v8::Local<v8::Value>();
         return val;
 }