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Unfortunately, this bug was introduced in the latest version.

The crash happens when you try to delete the currently open file. As a workaround, you can close the file first and then delete it: 
http://www.textasticapp.com/v4/manual/lessons/How_can_I_show_a_list_of_recently_opened_files_How_can_I_close_the_current_file.html


I will fix it in the next version.
It shouldn't. Which version do you use? Which iPad? 

I'll consider it. It just never happened to me that I accidentally started zooming.
This already exists in the form of the symbol list.
I use it to quickly navigate in a large file: zoom down to 25% to get an overview of the file. Then zoom in to the part you want to edit. The zoom snaps to 100%, so it should be relatively easy to do.
How do you zoom accidentally? I want to add as few settings as possible.
This is the default behavior in iOS. Try it for example in Apple's Notes app.

To bring up the keyboard, tap on the editor once. You can then select text while the keyboard is open.

If instead you double-tap on the editor to select text while the keyboard is closed, the keyboard will not come up - you will only be able to copy the selected text. This is done so you can just copy some text without bringing up the keyboard.

It's still on my todo list. As a workaround, you can use an SSH app like Prompt or iSSH in addition to Textastic.