MDL-34549 libraries: Changing strictness of context::instance_by_id() when required

blocks/html/block_html.php

@@ -104,7 +104,7 @@ class block_html extends block_base {
     function content_is_trusted() {
         global $SCRIPT;
 
-        if (!$context = context::instance_by_id($this->instance->parentcontextid)) {
+        if (!$context = context::instance_by_id($this->instance->parentcontextid, IGNORE_MISSING)) {
             return false;
         }
         //find out if this block is on the profile page

blocks/html/lib.php

@@ -53,7 +53,7 @@ function block_html_pluginfile($course, $birecord_or_cm, $context, $filearea, $a
         send_file_not_found();
     }
 
-    if ($parentcontext = context::instance_by_id($birecord_or_cm->parentcontextid)) {
+    if ($parentcontext = context::instance_by_id($birecord_or_cm->parentcontextid, IGNORE_MISSING)) {
         if ($parentcontext->contextlevel == CONTEXT_USER) {
             // force download on all personal pages including /my/
             //because we do not have reliable way to find out from where this is used