sexp: Add missing free on error path

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>

diff --git a/grub-core/lib/libgcrypt/src/sexp.c b/grub-core/lib/libgcrypt/src/sexp.c
index d15f1a790..250559f75 100644
--- a/grub-core/lib/libgcrypt-grub/src/sexp.c
+++ b/grub-core/lib/libgcrypt-grub/src/sexp.c
@@ -1157,6 +1157,17 @@ do_vsexp_sscan (gcry_sexp_t *retsexp, size_t *erroff,
                               }                                            \
                        } while (0)
 
+#define MAKE_SPACE_EXTRA_CLEANUP(n, cleanup)  do {				\
+                            gpg_err_code_t _ms_err = make_space (&c, (n)); \
+                            if (_ms_err)                                   \
+                              {                                            \
+                                err = _ms_err;                             \
+                                *erroff = p - buffer;                      \
+				cleanup;				   \
+                                goto leave;                                \
+                              }                                            \
+                       } while (0)
+
   /* The STORE_LEN macro is used to store the length N at buffer P. */
 #define STORE_LEN(p,n) do {						   \
 			    DATALEN ashort = (n);			   \
@@ -1368,7 +1379,7 @@ do_vsexp_sscan (gcry_sexp_t *retsexp, size_t *erroff,
                   goto leave;
                 }
 
-              MAKE_SPACE (datalen);
+              MAKE_SPACE_EXTRA_CLEANUP (datalen, xfree (b64buf));
               *c.pos++ = ST_DATA;
               STORE_LEN (c.pos, datalen);
               for (i = 0; i < datalen; i++)