Get rid of most instance of 'foo == NULL'

core/src/fxge/win32/fx_win32_dwrite.cpp

Index: core/src/fxge/win32/fx_win32_dwrite.cpp
diff --git a/core/src/fxge/win32/fx_win32_dwrite.cpp b/core/src/fxge/win32/fx_win32_dwrite.cpp
index 83924f23e7e1780169fdb686ef18f6acbe915663..9e56ee767265fec6f43977615346703bfe403852 100644
--- a/core/src/fxge/win32/fx_win32_dwrite.cpp
+++ b/core/src/fxge/win32/fx_win32_dwrite.cpp
@@ -65,7 +65,7 @@ class CDwFontFileLoader final : public IDWriteFontFileLoader {
                       OUT IDWriteFontFileStream** fontFileStream);
 
   static IDWriteFontFileLoader* GetLoader() {
-    if (instance_ == NULL) {
+    if (!instance_) {
       instance_ = new CDwFontFileLoader();
     }
     return instance_;
@@ -216,7 +216,7 @@ FX_BOOL CDWriteExt::DwRendingString(void* renderTarget,
                                     FX_FLOAT baselineOriginY,
                                     void* glyph_offsets,
                                     FX_FLOAT* glyph_advances) {
-  if (renderTarget == NULL) {
+  if (!renderTarget) {
     return TRUE;
   }
   CDwGdiTextRenderer* pTextRenderer = (CDwGdiTextRenderer*)renderTarget;