Don’t close the cURL handle more than once

When close() was called more than once PHP warnings appeared stating that "XY is not a valid cURL handle resource". This was especially problematic when close() was called manually because it will also *always* be called from the destructor. From no on we’ll first check whether $this->curl is still a resource to avoid that.

Author: J5lx

src/Curl/Curl.php

@@ -121,7 +121,9 @@ public function verbose($on=TRUE) {
 	}
 
 	public function close() {
-		curl_close($this->curl);
+		if (is_resource($this->curl)) {
+			curl_close($this->curl);
+		}
 	}
 
 	public function _exec() {