close correctly `span` tag in `oembed_format_object()`

fix issue #1612

include/oembed.php

@@ -193,8 +193,9 @@ function oembed_format_object($j){
 	} else {
 		// add <a> for html2bbcode conversion
 		$ret .= "<a href='$embedurl' rel='oembed'>$embedurl</a>";
-		$ret.="<br style='clear:left'></span>";
+		$ret .= "<br style='clear:left'>";
 	}
+	$ret.="</span>";
 	return  mb_convert_encoding($ret, 'HTML-ENTITIES', mb_detect_encoding($ret));
 }