Fix an assertion failure in CPDFSDK_Widget* Field::GetWidget()

fpdfsdk/src/javascript/Field.cpp

Index: fpdfsdk/src/javascript/Field.cpp
diff --git a/fpdfsdk/src/javascript/Field.cpp b/fpdfsdk/src/javascript/Field.cpp
index 39e15e9868bb32fc7671442b8ee0104b6c9a8f3b..40af4103e2c637f13fa9512f783e9bdd9c4b4419 100644
--- a/fpdfsdk/src/javascript/Field.cpp
+++ b/fpdfsdk/src/javascript/Field.cpp
@@ -289,13 +289,10 @@ void Field::UpdateFormControl(CPDFSDK_Document* pDocument,
 
 CPDFSDK_Widget* Field::GetWidget(CPDFSDK_Document* pDocument,
                                  CPDF_FormControl* pFormControl) {
-  ASSERT(pDocument != NULL);
-  ASSERT(pFormControl != NULL);
-
-  CPDFSDK_InterForm* pInterForm = (CPDFSDK_InterForm*)pDocument->GetInterForm();
-  ASSERT(pInterForm != NULL);
-
-  return pInterForm->GetWidget(pFormControl);
+  ASSERT(pDocument);

[Tom Sepez, 2015/11/30 17:19:11]

Nit: we can remove this assert because pDocument->GetInterForm() will segv if
pDocument is null, so we get the equivalent assertion from the hardware for free
without adding any instructions.

[jun_fang, 2015/12/01 04:30:12]

Acknowledged.

+  CPDFSDK_InterForm* pInterForm =
+      static_cast<CPDFSDK_InterForm*>(pDocument->GetInterForm());
+  return pInterForm ? pInterForm->GetWidget(pFormControl) : nullptr;
 }
 
 FX_BOOL Field::ValueIsOccur(CPDF_FormField* pFormField,