error installing additional drivers

installArchives() failed:
Extracting templates from packages: 56%
Extracting templates from packages: 100%

Extracting templates from packages: 56%
Extracting templates from packages: 100%

Extracting templates from packages: 56%
Extracting templates from packages: 100%

Extracting templates from packages: 56%
Extracting templates from packages: 100%
(Reading database ...
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(Reading database ... 95%
(Reading database ... 100%
(Reading database ... 187391 files and directories currently installed.)
Removing linux-image-extra-3.11.0-12-generic ...
Examining /etc/kernel/postrm.d .
run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.11.0-12-generic /boot/vmlinuz-3.11.0-12-generic
update-initramfs: Deleting /boot/initrd.img-3.11.0-12-generic
run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.11.0-12-generic /boot/vmlinuz-3.11.0-12-generic
/usr/sbin/grub-mkconfig: 35: /etc/default/grub: Syntax error: EOF in backquote substitution
run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 2
Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-extra-3.11.0-12-generic.postrm line 328.
dpkg: error processing linux-image-extra-3.11.0-12-generic (--remove):
 subprocess installed post-removal script returned error exit status 1
No apport report written because MaxReports is reached already
Removing linux-image-3.11.0-12-generic ...
Examining /etc/kernel/postrm.d .
run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.11.0-12-generic /boot/vmlinuz-3.11.0-12-generic
update-initramfs: Deleting /boot/initrd.img-3.11.0-12-generic
run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.11.0-12-generic /boot/vmlinuz-3.11.0-12-generic
/usr/sbin/grub-mkconfig: 35: /etc/default/grub: Syntax error: EOF in backquote substitution
run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 2
Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-3.11.0-12-generic.postrm line 328.
dpkg: error processing linux-image-3.11.0-12-generic (--remove):
 subprocess installed post-removal script returned error exit status 1
No apport report written because MaxReports is reached already
Errors were encountered while processing:
 linux-image-extra-3.11.0-12-generic
 linux-image-3.11.0-12-generic