MDL-39305 fixed display bugs in course listings

- When category has a lot of subcategories and courses and user clicks 'view more' for categories, the courses are still displayed
- Course summary non-image files may appear above course summary image files, and they don't have an icon with the filetype
MDL-39306 fix course search regression

Oracle handling of NULLs is totally wrong and crazy!
Merge branch 'MDL-39296-master' of git://github.com/ankitagarwal/moodle
Merge branch 'MDL-37784' of git://github.com/jmvedrine/moodle
MDL-39219 mod_scorm - make sure YUI JSON module is loaded
Merge branch 'wip-MDL-38441-m25' of git://github.com/samhemelryk/moodle
Merge branch 'w16_MDL-38972_m25_oraindex' of git://github.com/skodak/moodle
MDL-38972 xmldb: amend comments.
MDL-39326 css: no passed the no svg key to chunking when required
MDL-39326 css: removed unused chunk array search
MDL-38851 Admin: Fixed setType notice for webservice
MDL-38851 Admin: Fixed setType notice for cache
Merge branch 'wip-mdl-38851' of git://github.com/rajeshtaneja/moodle
MDL-39329 course: Strict standard warning during unpublishing
Merge branch 'wip-MDL-39326-m25' of git://github.com/samhemelryk/moodle
MDL-32946 - Blocks - Improving image alts for accessibility.
MDL-38892 data module: Fixed action setType to use PARAM_ALPHANUM
MDL-39192 mod_forum: do not need to check the posting threshold when editing a post
Merge branch 'MDL-34939-master' of https://github.com/lucisgit/moodle
Merge branch 'MDL-38892' of git://github.com/rwijaya/moodle