mesa: fix ES only draw if we have vertex positions

This code was separated from the validation code so it could
use used with KHR_no_error paths. The return values were inverted
to reflect the name of the helper, but here the condtion was
mistakenly inverted rather than the return value.

Fixes: 4df2931a87 (mesa/vbo: move some Draw checks out of validation)

Reported-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/mesa/vbo/vbo_exec_array.c

@@ -193,8 +193,8 @@ skip_validated_draw(struct gl_context *ctx)
    case API_OPENGLES:
       /* For OpenGL ES, only draw if we have vertex positions
        */
-      if (ctx->Array.VAO->VertexAttrib[VERT_ATTRIB_POS].Enabled)
-         return false;
+      if (!ctx->Array.VAO->VertexAttrib[VERT_ATTRIB_POS].Enabled)
+         return true;
       break;
 
    case API_OPENGL_CORE: