消除 &NSLinkAttributeName 总是true的编译警告

[KathenZK]

Eliminate the compiler warnings for "if (&NSLinkAttributeName)" is always true.

[codecov-io]

Current coverage is 89.14%

Merging #652 into master will not affect coverage as of 4bc7415

@@            master    #652   diff @@
======================================
  Files            2       2       
  Stmts         1087    1087       
  Branches         0       0       
  Methods                          
======================================
  Hit            969     969       
  Partial          0       0       
  Missed         118     118       

Review entire Coverage Diff as of 4bc7415

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