Disable the else clause which assigns the default fragment program to ctx->FragmentProgram._Current

The _Current field should either point to the fragment program which is to be
run (GLSL, ARB_f_p, fixed-func-generated, etc) or be NULL if conventional
fixed-function code is to be used.  Matches TNL program code.

src/mesa/main/texenvprogram.c

@@ -1279,9 +1279,11 @@ _mesa_UpdateTexEnvProgram( GLcontext *ctx )
             _mesa_printf("Found existing texenv program for key %x\n", hash);
       }
    } 
+#if 0
    else {
       ctx->FragmentProgram._Current = ctx->FragmentProgram.Current;
    }
+#endif
 
    /* Tell the driver about the change.  Could define a new target for
     * this?