Codechange: Split GetGroup into GetGroup/GetOrCreateGroup.

This follows the pattern used for GetItem/GetOrCreateItem, and allows use
of references where we know the group must exist.

src/ini_load.cpp

@@ -193,6 +193,21 @@ IniGroup *IniLoadFile::GetGroup(const std::string &name, bool create_new)
 	return &this->CreateGroup(name);
 }
 
+/**
+ * Get the group with the given name, and if it doesn't exist create a new group.
+ * @param name name of the group to find.
+ * @return the requested group.
+ */
+IniGroup &IniLoadFile::GetOrCreateGroup(const std::string &name)
+{
+	for (IniGroup *group = this->group; group != nullptr; group = group->next) {
+		if (group->name == name) return *group;
+	}
+
+	/* Group doesn't exist, make a new one. */
+	return this->CreateGroup(name);
+}
+
 /**
  * Create an group with the given name. This does not reuse an existing group of the same name.
  * @param name name of the group to create.