Merge pull request repejota#91 from dfeyer/patch-3

TASK: Close should check if the current socket is null

Author: repejota

src/Nats/Connection.php

@@ -495,6 +495,9 @@ public function setChunkSize($chunkSize)
      */
     public function close()
     {
+        if ($this->streamSocket === null) {
+            return;
+        }
         fclose($this->streamSocket);
         $this->streamSocket = null;
     }