Fix clang analyzer warning
Fix clang analyzer warning

redisAsyncInitialize() can return NULL, but then we pass
the return value from redisAsyncInitialize() into something
dereferencing the return value, which can cause crashies.

nokiddin/hiredis,tattsun/hiredis,rangan337/hiredis,thomaslee/hiredis,badboy/hiredis-win,liulingfree/hiredis,owent-contrib/hiredis,galdor/hiredis,picrin/redisSamples,galdor/hiredis,jqk6/hiredis,jinguoli/hiredis,olgeni/hiredis,owent-contrib/hiredis,arinal/hiredis,hidebug/hiredis,xjzhou/hiredis,chenlicong0821/hiredis,charsyam/hiredis,yiliaofan/hiredis,rangan337/hiredis,redis/hiredis,charsyam/hiredis,h1048576/hiredis,olgeni/hiredis,jinguoli/hiredis,hidebug/hiredis,thomaslee/hiredis,xjzhou/hiredis,jinguoli/hiredis,redis/hiredis,redis/hiredis,tattsun/hiredis,liulingfree/hiredis,Yhgenomics/hiredis,Yhgenomics/hiredis,chenlicong0821/hiredis