[QRA] Check length of the gridsquare isn't greater than 6 chars

This fixes #934 as Cloudlog bearings only works for squares that are less than 6 chars.

application/libraries/Qra.php

@@ -23,6 +23,7 @@ class Qra {
 	
 	// calculate  the bearing between two squares
 	function bearing($tx, $rx, $unit = 'M') {
+		if(strlen($tx) <= 6 && strlen($rx) <= 6) {
 			$my = qra2latlong($tx);
 			$stn = qra2latlong($rx);
 
@@ -30,6 +31,7 @@ class Qra {
 			
 			return $bearing;
 		}
+	}
 
 	/*
 	* Function: calculate the distance between two gridsqaures