Adjust null object check

core/src/fpdfdoc/doc_formfield.cpp

Index: core/src/fpdfdoc/doc_formfield.cpp
diff --git a/core/src/fpdfdoc/doc_formfield.cpp b/core/src/fpdfdoc/doc_formfield.cpp
index e51acf94a111a5216045773ba04e45fe918db420..eeba372390e348b928682674ef36286ff3b9ae34 100644
--- a/core/src/fpdfdoc/doc_formfield.cpp
+++ b/core/src/fpdfdoc/doc_formfield.cpp
@@ -1077,9 +1077,12 @@ FX_BOOL CPDF_FormField::ClearSelectedOptions(FX_BOOL bNotify)
 }
 void CPDF_FormField::LoadDA()
 {
-    CFX_ByteString DA = FPDF_GetFieldAttr(m_pDict, "DA") ? FPDF_GetFieldAttr(m_pDict, "DA")->GetString() : CFX_ByteString();
-    if (DA.IsEmpty()) {
-        DA = m_pForm->m_pFormDict ? m_pForm->m_pFormDict->GetString("DA") : CFX_ByteString();
+    CFX_ByteString DA;
+    if (CPDF_Object* pObj_t = FPDF_GetFieldAttr(m_pDict, "DA")) {
+        DA = pObj_t->GetString();
+    }
+    if (DA.IsEmpty() && m_pForm->m_pFormDict) {
+        DA = m_pForm->m_pFormDict->GetString("DA");
     }
     if (DA.IsEmpty()) {
         return;