check a feature has a valid start and end

modules/Bio/EnsEMBL/Feature.pm

@@ -122,9 +122,13 @@ sub new {
   }
 
   if(defined($start) && defined($end)) {
-    if($end+1 < $start) {
-      throw('Start must be less than or equal to end+1');
-    }
+      if (($start =~ /\d+/) && ($end =~ /\d+/)) {
+	  if($end+1 < $start) {
+	      throw('Start must be less than or equal to end+1');
+	  }
+      } else {
+	      throw('Start and end must be integers');
+      }
   }
 
   return bless({'start'    => $start,