applied patch from Alfred Mickautsch fixing #125180 Daniel

* xmlwriter.c: applied patch from Alfred Mickautsch fixing #125180
Daniel
diff --git a/xmlwriter.c b/xmlwriter.c
index 0e2a979..21897ee 100644
--- a/xmlwriter.c
+++ b/xmlwriter.c
@@ -1117,6 +1117,9 @@
 
             linelen += 4;
         }
+
+        if (i >= len)
+            break;
     }
 
     count = xmlOutputBufferWrite(out, 2, B64CRLF);