Skip invalid commands when constructing the toolbar and menu rather than exploding

Originally committed to SVN as r5478.

aegisub/src/menu.cpp

@@ -100,7 +100,14 @@ wxMenu* Menu::BuildMenu(std::string name, const json::Array& array, int submenu)
 
 
 		std::string cmd_name = type == Menu::Submenu ? name_submenu : command.Value();
-		cmd::Command *cmd = cmd::get(cmd_name);
+		cmd::Command *cmd;
+		try {
+			cmd = cmd::get(cmd_name);
+		}
+		catch (CommandNotFound const&) {
+			LOG_W("menu/command/not_found") << "Command '" << cmd_name << "' not found; skipping";
+			continue;
+		}
 
 		wxString display = cmd->StrMenu() + "\t" + hotkey::get_hotkey_str_first("Default", cmd_name);
 		wxString descr = cmd->StrHelp();

aegisub/src/toolbar.cpp

@@ -33,6 +33,7 @@
 #endif
 
 #include <libaegisub/json.h>
+#include <libaegisub/log.h>
 #include <libaegisub/signal.h>
 
 namespace {
@@ -105,7 +106,14 @@ namespace {
 					AddSeparator();
 				}
 				else {
-					cmd::Command *command = cmd::get(command_name.Value());
+					cmd::Command *command;
+					try {
+						command = cmd::get(command_name.Value());
+					}
+					catch (CommandNotFound const&) {
+						LOG_W("toolbar/command/not_found") << "Command '" << command_name.Value() << "' not found; skipping";
+						continue;
+					}
 
 					wxBitmap const& bitmap = command->Icon(icon_size);
 					// this hack is needed because ???