Move glTexSubImage early out check after more of the error checks are done.

src/libGLESv2/libGLESv2.cpp

@@ -5623,11 +5623,6 @@ void __stdcall glTexSubImage2D(GLenum target, GLint level, GLint xoffset, GLint
             return error(GL_INVALID_ENUM);
         }
 
-        if (width == 0 || height == 0 || pixels == NULL)
-        {
-            return;
-        }
-
         gl::Context *context = gl::getNonLostContext();
 
         if (context)
@@ -5665,6 +5660,11 @@ void __stdcall glTexSubImage2D(GLenum target, GLint level, GLint xoffset, GLint
                 return error(GL_INVALID_OPERATION);
             }
 
+            if (width == 0 || height == 0 || pixels == NULL)
+            {
+                return;
+            }
+
             if (target == GL_TEXTURE_2D)
             {
                 gl::Texture2D *texture = context->getTexture2D();