Fix the issue that no response from the call back function of FFI_GetPlatform()

fpdfsdk/src/javascript/app.cpp

Index: fpdfsdk/src/javascript/app.cpp
diff --git a/fpdfsdk/src/javascript/app.cpp b/fpdfsdk/src/javascript/app.cpp
index d18e0322abff79c17035657eb85f9a354cc11913..3f1a3b7648079be629f5150d9bb7be0411ba926c 100644
--- a/fpdfsdk/src/javascript/app.cpp
+++ b/fpdfsdk/src/javascript/app.cpp
@@ -217,12 +217,23 @@ FX_BOOL app::viewerVersion(IJS_Context* cc,
 FX_BOOL app::platform(IJS_Context* cc,
                       CJS_PropValue& vp,
                       CFX_WideString& sError) {
-  if (vp.IsGetting()) {
+  if (!vp.IsGetting())
+    return FALSE;
+  CJS_Context* pContext = static_cast<CJS_Context*>(cc);
+  if (!pContext)

[Tom Sepez, 2015/11/30 17:17:32]

Can these ever be NULL?  

[jun_fang, 2015/12/01 10:53:30]

pContext is passed from v8. It shouldn't be nullptr.

+    return FALSE;
+  CJS_Runtime* pRuntime = pContext->GetJSRuntime();
+  if (!pRuntime)

[jun_fang, 2015/12/01 10:53:30]

pRuntime shouldn't be nullptr either.

+    return FALSE;
+  CPDFDoc_Environment* pEnv = pRuntime->GetReaderApp();
+  if (!pEnv)

[jun_fang, 2015/12/01 10:53:30]

pEnv can be nullptr. 

+    return FALSE;
+  CFX_WideString platfrom = pEnv->FFI_GetPlatform();
+  if (platfrom.IsEmpty())
     vp << JS_STR_PLATFORM;
-    return TRUE;
-  }
-
-  return FALSE;
+  else
+    vp << platfrom;
+  return TRUE;
 }
 
 FX_BOOL app::language(IJS_Context* cc,