- fix blinking caused by uninitialized clipping planes

wadsrc/static/shaders/glsl/main.vp

@@ -116,4 +116,10 @@ void main()
 	// clip planes used for translucency splitting
 	gl_ClipDistance[1] = worldcoord.y - uClipSplit.x;
 	gl_ClipDistance[2] = uClipSplit.y - worldcoord.y;
+
+	if (uSplitTopPlane == vec4(0.0))
+	{
+		gl_ClipDistance[3] = 1;
+		gl_ClipDistance[4] = 1;
+	}
 }