Clean up.

Author: mrdoob

src/renderers/webgl/WebGLTextures.js

@@ -1644,7 +1644,7 @@ function WebGLTextures( _gl, extensions, state, properties, capabilities, utils,
 	// Setup resources for a Depth Texture for a FBO (needs an extension)
 	function setupDepthTexture( framebuffer, renderTarget, cubeFace ) {
 
-		const isCube = ( renderTarget && renderTarget.isWebGLCubeRenderTarget );
+		const isCube = ( renderTarget.isWebGLCubeRenderTarget === true );
 
 		state.bindFramebuffer( _gl.FRAMEBUFFER, framebuffer );