Quote around variables to avoid miserably crashing if variable is empty

scripts/upgrade

@@ -49,7 +49,7 @@ fi
 current_version=$(grep OC_VersionString "$final_path/version.php" | cut -d\' -f2)
 current_major_version=${current_version%%.*}
 
-if [ $current_major_version -gt 11 ]
+if [ "$current_major_version" -gt 11 ]
 then
     # Inform the backup/restore process that it should not save the data directory
     ynh_app_setting_set $app backup_core_only 1
@@ -73,7 +73,7 @@ ynh_abort_if_errors
 #=================================================
 
 ynh_handle_app_migration "owncloud" "owncloud_migration"
-if [ $migration_process -eq 1 ]
+if [ "$migration_process" -eq 1 ]
 then
     # If a migration has been perform
     # Reload some values changed by the migration process
@@ -270,7 +270,7 @@ exec_occ config:system:get logout_url >/dev/null 2>&1 \
 #=================================================
 
 # Enable External Storage and create local mount to home folder as needed
-if [ $user_home -eq 1 ]; then
+if [ "$user_home" -eq 1 ]; then
     exec_occ app:enable files_external
     exec_occ files_external:list --output=json \
 	| grep -q '"storage":"\\\\OC\\\\Files\\\\Storage\\\\Local"' \
@@ -372,7 +372,7 @@ systemctl reload nginx
 # FINISH MIGRATION PROCESS
 #=================================================
 
-if [ $migration_process -eq 1 ]
+if [ "$migration_process" -eq 1 ]
 then
     echo "ownCloud has been successfully migrated to Nextcloud! \
 A last scheduled operation will run in a couple of minutes to finish the \