Fail on get_chainactive before lock if checks fail

src/miner.cpp

@@ -813,11 +813,13 @@ int32_t waitForPeers(const CChainParams &chainparams)
 #ifdef ENABLE_WALLET
 CBlockIndex *get_chainactive(int32_t height)
 {
-    LOCK(cs_main);
-    if ( chainActive.Tip() != 0 )
+    if ( chainActive.LastTip() != 0 )
     {
-        if ( height <= chainActive.Tip()->nHeight )
+        if ( height <= chainActive.LastTip()->nHeight )
+        {
+            LOCK(cs_main);
             return(chainActive[height]);
+        }
         // else fprintf(stderr,"get_chainactive height %d > active.%d\n",height,chainActive.Tip()->nHeight);
     }
     //fprintf(stderr,"get_chainactive null chainActive.Tip() height %d\n",height);