Fixed building when defining ImTextureID to a multi-token name. (#1641)

Amend 92b9498

imgui_draw.cpp

@@ -619,7 +619,7 @@ void ImDrawList::PushTextureID(ImTextureID texture_id)
 void ImDrawList::PopTextureID()
 {
     _TextureIdStack.pop_back();
-    _CmdHeader.TextureId = (_TextureIdStack.Size == 0) ? ImTextureID() : _TextureIdStack.Data[_TextureIdStack.Size - 1];
+    _CmdHeader.TextureId = (_TextureIdStack.Size == 0) ? (ImTextureID)NULL : _TextureIdStack.Data[_TextureIdStack.Size - 1];
     _OnChangedTextureID();
 }
 
@@ -2777,7 +2777,7 @@ static bool ImFontAtlasBuildWithStbTruetype(ImFontAtlas* atlas)
     ImFontAtlasBuildInit(atlas);
 
     // Clear atlas
-    atlas->TexID = ImTextureID();
+    atlas->TexID = (ImTextureID)NULL;
     atlas->TexWidth = atlas->TexHeight = 0;
     atlas->TexUvScale = ImVec2(0.0f, 0.0f);
     atlas->TexUvWhitePixel = ImVec2(0.0f, 0.0f);