Fixed enter in modal confirmation dialogs

Fixes #463
Fixes #464

(cherry picked from commit 930742ae2c69a530afe60f76a5824f2722540df8)

frontend/src/Components/Modal/ConfirmModal.js

@@ -30,10 +30,10 @@ function ConfirmModal(props) {
   useEffect(() => {
     if (isOpen) {
       bindShortcut('enter', onConfirm);
-    } else {
-      unbindShortcut('enter', onConfirm);
+
+      return () => unbindShortcut('enter', onConfirm);
     }
-  }, [onConfirm]);
+  }, [isOpen, onConfirm]);
 
   return (
     <Modal

frontend/src/Components/keyboardShortcuts.js

@@ -56,8 +56,10 @@ function keyboardShortcuts(WrappedComponent) {
     }
 
     unbindShortcut = (key) => {
-      delete this._mousetrapBindings[key];
-      this._mousetrap.unbind(key);
+      if (this._mousetrap != null) {
+        delete this._mousetrapBindings[key];
+        this._mousetrap.unbind(key);
+      }
     }
 
     unbindAllShortcuts = () => {