fix(tipc): remove filtered-out elements

Since the removal of elements are performed by "${params[@]/$i/}" in
the above loops, the removed elements remain in the array `params` as
empty elements.  Therefore, we need to remove the empty elements by
specifying `-X ''`.  This is a regression by
#887.  These empty
elements were originally automatically dropped by unquoted
${params[@]}.

Reference:
13c28e9#diff-62e0a63a79957c52fe6b79be0a66a987da044839c6bcaeaa725fcd199c4e528fR160

completions/tipc

@@ -153,7 +153,7 @@ _comp_cmd_tipc()
                         done
                     done
 
-                    _comp_compgen -- -W '"${params[@]}"'
+                    _comp_compgen -- -W '"${params[@]}"' -X ''
                     ;;
                 disable)
                     ((optind++))