Docs:little fix in zh doc

docs/api/zh/renderers/WebGLRenderer.html

@@ -395,7 +395,7 @@
 
 		<h3>[method:null setRenderTarget]( [param:WebGLRenderTarget renderTarget], [param:Integer activeCubeFace], [param:Integer activeMipmapLevel] )</h3>
 		<p>
-		renderTarget -- 需要被激活的[page:WebGLRenderTarget renderTarget](可选)。When *null* is given, the canvas is set as the active render target instead.<br />
+		renderTarget -- 需要被激活的[page:WebGLRenderTarget renderTarget](可选)。若此参数为空，则将canvas设置成活跃render target。<br />
 		activeCubeFace -- Specifies the active cube side (PX 0, NX 1, PY 2, NY 3, PZ 4, NZ 5) of [page:WebGLRenderTargetCube] (optional).<br />
 		activeMipmapLevel -- Specifies the active mipmap level (optional).<br /><br />
 		该方法设置活跃rendertarget。