vvfat: Fix memory leak

Don't leak 'cluster' in the mapping == NULL case. Found by Coverity
(CID 1055918).

Fixes: 8d9401c2Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NLiam Merwick <liam.merwick@oracle.com>
Tested-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>

block/vvfat.c

@@ -2510,7 +2510,7 @@ static int commit_one_file(BDRVVVFATState* s,
     uint32_t first_cluster = c;
     mapping_t* mapping = find_mapping_for_cluster(s, c);
     uint32_t size = filesize_of_direntry(direntry);
-    char* cluster = g_malloc(s->cluster_size);
+    char *cluster;
     uint32_t i;
     int fd = 0;
 
@@ -2528,17 +2528,17 @@ static int commit_one_file(BDRVVVFATState* s,
     if (fd < 0) {
         fprintf(stderr, "Could not open %s... (%s, %d)\n", mapping->path,
                 strerror(errno), errno);
-        g_free(cluster);
         return fd;
     }
     if (offset > 0) {
         if (lseek(fd, offset, SEEK_SET) != offset) {
             qemu_close(fd);
-            g_free(cluster);
             return -3;
         }
     }
 
+    cluster = g_malloc(s->cluster_size);
+
     while (offset < size) {
         uint32_t c1;
         int rest_size = (size - offset > s->cluster_size ?