patch 7.4.1278

Problem:    When jsonencode() fails it still returns something.
Solution:   Return an empty string on failure.

src/version.c

@@ -747,6 +747,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1278,
 /**/
     1277,
 /**/