Fix uninitialised API structure boolean fields

They were causing intermittent test failures.

include/loot/struct/masterlist_info.h

@@ -32,6 +32,8 @@ namespace loot {
  *        revision.
  */
 struct MasterlistInfo {
+  inline MasterlistInfo() : is_modified(false) {}
+
   /**
    * @brief The revision hash for the masterlist. If the masterlist doesn't
    *        exist, or there is no Git repository at its location, this will be

include/loot/struct/plugin_tags.h

@@ -33,6 +33,8 @@ namespace loot {
  *        LOOT for a plugin.
  */
 struct PluginTags {
+  inline PluginTags() : userlist_modified(false) {}
+
   /**
    * @brief A set of Bash Tag names suggested for addition to the specified
    *        plugin. Empty if no Bash Tag additions are suggested.