Properly fix the warnings

ASSERT(statement) will not execute statement in release builds. So
need to move statements outside ASSERT().

TBR=tsepez@chromium.org,dsinclair@chromium.org

Review URL: https://codereview.chromium.org/1949613004 .
diff --git a/xfa/fxfa/parser/xfa_object_imp.cpp b/xfa/fxfa/parser/xfa_object_imp.cpp
index 32da7f7..91497a5 100644
--- a/xfa/fxfa/parser/xfa_object_imp.cpp
+++ b/xfa/fxfa/parser/xfa_object_imp.cpp
@@ -4574,7 +4574,8 @@
 int32_t CXFA_Node::InsertChild(int32_t index, CXFA_Node* pNode) {
   ASSERT(!pNode->m_pNext);
   pNode->m_pParent = this;
-  ASSERT(m_pDocument->RemovePurgeNode(pNode));
+  FX_BOOL ret = m_pDocument->RemovePurgeNode(pNode);
+  ASSERT(ret);
 
   if (m_pChild == NULL || index == 0) {
     if (index > 0) {
@@ -4622,7 +4623,8 @@
     ASSERT(false);
     return FALSE;
   }
-  ASSERT(m_pDocument->RemovePurgeNode(pNode));
+  FX_BOOL ret = m_pDocument->RemovePurgeNode(pNode);
+  ASSERT(ret);
 
   int32_t nIndex = -1;
   pNode->m_pParent = this;