fix a few linux compilation warnings

core/src/fpdfapi/fpdf_edit/fpdf_edit_image.cpp

Index: core/src/fpdfapi/fpdf_edit/fpdf_edit_image.cpp
diff --git a/core/src/fpdfapi/fpdf_edit/fpdf_edit_image.cpp b/core/src/fpdfapi/fpdf_edit/fpdf_edit_image.cpp
index d73d7614dadc9d4e0b1967defd00e7229d86359f..d2f2c5072fc2ba4d5657beeb09f6f1078bed2029 100644
--- a/core/src/fpdfapi/fpdf_edit/fpdf_edit_image.cpp
+++ b/core/src/fpdfapi/fpdf_edit/fpdf_edit_image.cpp
@@ -195,9 +195,13 @@ void CPDF_Image::SetImage(const CFX_DIBitmap* pBitmap, FX_INT32 iCompress, IFX_F
             opType = 0;
         }
     }
+    FX_BOOL bDeleteMask = FALSE;
     const CFX_DIBitmap* pMaskBitmap = NULL;
     if (pBitmap->HasAlpha()) {
         pMaskBitmap = pBitmap->GetAlphaMask();
+        if (pMaskBitmap) {
+          bDeleteMask = TRUE;
+        }
     }
     if (!pMaskBitmap && pMask) {
         FXDIB_Format maskFormat = pMask->GetFormat();
@@ -210,7 +214,6 @@ void CPDF_Image::SetImage(const CFX_DIBitmap* pBitmap, FX_INT32 iCompress, IFX_F
         FX_INT32 maskHeight = pMaskBitmap->GetHeight();
         FX_LPBYTE mask_buf = NULL;
         FX_STRSIZE mask_size;
-        FX_BOOL bDeleteMask = TRUE;
         CPDF_Dictionary* pMaskDict = FX_NEW CPDF_Dictionary;
         pMaskDict->SetAtName(FX_BSTRC("Type"), FX_BSTRC("XObject"));
         pMaskDict->SetAtName(FX_BSTRC("Subtype"), FX_BSTRC("Image"));
@@ -243,10 +246,9 @@ void CPDF_Image::SetImage(const CFX_DIBitmap* pBitmap, FX_INT32 iCompress, IFX_F
             }
             pMaskStream = FX_NEW CPDF_Stream(mask_buf, mask_size, pMaskDict);
             m_pDocument->AddIndirectObject(pMaskStream);
-            bDeleteMask = FALSE;
             pDict->SetAtReference(FX_BSTRC("SMask"), m_pDocument, pMaskStream);
         }
-        if (pBitmap->HasAlpha()) {
+        if (bDeleteMask) {
             delete pMaskBitmap;
         }
     }