[libxml2] Make xmlFuzzReadString return a zero size in error case

[Nick Wellnhofer <nwellnhof src gnome org>]

commit be889b658175606788de0a1ec1577cae80097694
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Wed Jan 26 16:35:18 2022 +0100

    Make xmlFuzzReadString return a zero size in error case
    
    Avoids use of uninitialized memory.

 fuzz/fuzz.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/fuzz/fuzz.c b/fuzz/fuzz.c
index 212136ac..be2f065b 100644
--- a/fuzz/fuzz.c
+++ b/fuzz/fuzz.c
@@ -185,6 +185,7 @@ xmlFuzzReadString(size_t *size) {
         return(out);
     }
 
+    *size = 0;
     return(NULL);
 }