test(): fix function call

Author: QHivert

SoObjects/SOGo/SOGoOpenIdSession.m

@@ -445,7 +445,12 @@ -(NSString *) _random_state
     int i = 0;
 
     for (i; i<10; i++) {
-         [randomState appendFormat: @"%C", [letters characterAtIndex: arc4random_uniform([letters length])]];
+      int r = 0;
+      if (arc4random_uniform != NULL)
+        r = arc4random_uniform([letters length]);
+      else
+        r = (arc4random() % [letters length]);
+      [randomState appendFormat: @"%C", [letters characterAtIndex: r]];
     }
 
     return randomState;