Guard against wiped-out match listing buffer in Neovim

If somebody deletes the Command-T match listing buffer on Neovim (eg.
with `:bwipeout`), Command-T will blow up on the next invocation because
Neovim doesn't define `Vim::DeletedBufferError`.

Closes: #342

Thanks to Javier Parra for the bug report with a minimal repro recipe
and diagnosis of the problem.

doc/command-t.txt

@@ -1560,6 +1560,7 @@ next (not yet released) ~
 - Fix edge cases with opening selections in tabs (#315).
 - Fix possible degenerate performance of |:CommandTBuffer| and
   |:CommandTMRU| on Neovim.
+- Handle missing match listing buffer in Neovim (#342).
 
 5.0.2 (7 September 2017) ~
 

ruby/command-t/lib/command-t/match_window.rb

@@ -154,9 +154,16 @@ def initialize(options = {})
 
     def buffer_number
       @@buffer && @@buffer.number
-    rescue Vim::DeletedBufferError
-      # Beware of people manually deleting Command-T's hidden, unlisted buffer.
-      @@buffer = nil
+    rescue StandardError => e
+      if (
+        defined?(Vim::DeletedBufferError) && e.instance_of?(Vim::DeletedBufferError) ||
+        e.message =~ /Invalid buffer/
+      )
+        # Something/someone deleted Command-T's hidden, unlisted buffer.
+        @@buffer = nil
+      else
+        raise
+      end
     end
 
     def close