Fix R key press cause web-ext to crash

[thamimemel]

Fixes : #1911 I reproduced the error unintentionally and found that there is an open issue for it, this patch fixes the bug but needs review for any side effects, or maybe code refactoring. The idea is to keep track of the reloading process in this.reloading and allow reloading only if it is false. IMPORTANT: please check if this works properly in android, i only tested in desktop.