[vim] Clean up temp files on interrupt (#2252)

The clean-up is done in s:collect(), so let's make sure it's run before
we may terminate due to CTRL-C or ESC (or some other error code) in
s:exit_handler().

plugin/fzf.vim

@@ -645,7 +645,8 @@ function! s:execute(dict, command, use_height, temps) abort
   endif
   let exit_status = v:shell_error
   redraw!
-  return s:exit_handler(exit_status, command) ? s:collect(a:temps) : []
+  let lines = s:collect(a:temps)
+  return s:exit_handler(exit_status, command) ? lines : []
 endfunction
 
 function! s:execute_tmux(dict, command, temps) abort
@@ -659,7 +660,8 @@ function! s:execute_tmux(dict, command, temps) abort
   call system(command)
   let exit_status = v:shell_error
   redraw!
-  return s:exit_handler(exit_status, command) ? s:collect(a:temps) : []
+  let lines = s:collect(a:temps)
+  return s:exit_handler(exit_status, command) ? lines : []
 endfunction
 
 function! s:calc_size(max, val, dict)
@@ -806,12 +808,12 @@ function! s:execute_term(dict, command, temps) abort
       execute self.winrest
     endif
 
+    let lines = s:collect(self.temps)
     if !s:exit_handler(a:code, self.command, 1)
       return
     endif
 
     call s:pushd(self.dict)
-    let lines = s:collect(self.temps)
     call s:callback(self.dict, lines)
     call self.switch_back(s:getpos() == self.ppos)
   endfunction