Work around MSVC bug 746973.

MSVC has a long history of value initialization bugs, and this one is
no exception. In this case, when some MSVC versions (at least up to
2013) are instructed to value-initialize a non-POD class with
a compiler generated non-trivial constructor, it does not zero out
the POD members.

src/render/rendergl1.cpp

@@ -181,7 +181,8 @@ public:
         std::weak_ptr<const Pixmap> texture;
     } current;
 
-    OpenGl1Renderer() : camera(), lighting(), current() {}
+    // List-initialize current to work around MSVC bug 746973.
+    OpenGl1Renderer() : camera(), lighting(), current({}) {}
 
     const Camera &GetCamera() const override { return camera; }
 

src/render/rendergl3.cpp

@@ -88,11 +88,12 @@ public:
         std::weak_ptr<const Pixmap> texture;
     } current;
 
+    // List-initialize current to work around MSVC bug 746973.
     OpenGl3Renderer() :
         lines(), meshes(), points(), pixmapCache(), masks(),
         initialized(), atlas(), meshRenderer(), imeshRenderer(),
         edgeRenderer(), outlineRenderer(), camera(), lighting(),
-        current() {}
+        current({}) {}
 
     void Init();