[rygel] engine-simple: Obey lseek return value

[Jens Georg <jensgeorg src gnome org>]

commit 4d02b78b5c897b5087396111f26c48f21e49246e
Author: Jens Georg <mail jensge org>
Date:   Wed Oct 2 00:01:24 2019 +0200

    engine-simple: Obey lseek return value
    
    Fixes #138

 src/media-engines/simple/rygel-simple-data-source.vala | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)
---
diff --git a/src/media-engines/simple/rygel-simple-data-source.vala 
b/src/media-engines/simple/rygel-simple-data-source.vala
index f99e3099..1fc74017 100644
--- a/src/media-engines/simple/rygel-simple-data-source.vala
+++ b/src/media-engines/simple/rygel-simple-data-source.vala
@@ -151,11 +151,19 @@ internal class Rygel.SimpleDataSource : DataSource, Object {
 
             if (this.last_byte == 0) {
                 this.last_byte = Posix.lseek (fd, 0, Posix.SEEK_END);
-                Posix.lseek (fd, 0, Posix.SEEK_SET);
+                if (this.last_byte < 0) {
+                    throw IOError.from_errno (errno);
+                }
+
+                if (Posix.lseek (fd, 0, Posix.SEEK_SET) < 0) {
+                    throw IOError.from_errno (errno);
+                }
+
             }
 
             if (this.first_byte != 0) {
-                 Posix.lseek (fd, this.first_byte, Posix.SEEK_SET);
+                 if (Posix.lseek (fd, this.first_byte, Posix.SEEK_SET) < 0)
+                    throw IOError.from_errno (errno);
             }
 
             while (true) {