winspool.drv: skip tests when no printer is installed

[Austin English]

Following the pattern in the rest of the file.

-- 
-Austin
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diff --git a/dlls/winspool.drv/tests/info.c b/dlls/winspool.drv/tests/info.c
index b81bde4..a31cbc9 100644
--- a/dlls/winspool.drv/tests/info.c
+++ b/dlls/winspool.drv/tests/info.c
@@ -1924,6 +1924,11 @@ static void test_SetDefaultPrinter(void)
     CHAR    buffer[DEFAULT_PRINTER_SIZE];
     CHAR    org_value[DEFAULT_PRINTER_SIZE];
 
+    if (!default_printer)
+    {
+        skip("There is no default printer installed\n");
+        return;
+    }
 
     if (!pSetDefaultPrinterA)  return;
 	/* only supported on win2k and above */