i965/vs: Return a dummy value when visiting ir_texture.

While the program won't successfully link in the end, this avoids
possible assertion failure in the driver during linking if
this->result isn't initialized with something already.

src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp

@@ -1675,6 +1675,7 @@ vec4_visitor::visit(ir_texture *ir)
     * programs that do vertex texturing, but after our visitor has
     * run.
     */
+   this->result = src_reg(this, glsl_type::vec4_type);
 }
 
 void