pb: Init fsize to make compiler happy

protobuf.c: In function ‘pb_show_msg’:
protobuf.c:384:68: error: ‘fsize’ may be used uninitialized in this function [-Werror=uninitialized]
protobuf.c:247:9: note: ‘fsize’ was declared here

The warning about 'may be uninitialized' is false -- the BUG() is a never-returning function.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

protobuf.c

@@ -244,7 +244,7 @@ static size_t pb_show_prepare_field_context(const ProtobufCFieldDescriptor *fd,
 					  pb_pr_ctl_t *ctl)
 {
 	pb_pr_field_t *field = &ctl->cur;
-	size_t fsize;
+	size_t fsize = 0;
 
 	switch (fd->type) {
 	case PROTOBUF_C_TYPE_ENUM: