fix(ssh): compare table length in the SSH config #41637

Problem:
`parse_ssh_config()` compares tables against a freshly allocated empty
table.
- In `parse_multiple_values()`, the guard which avoids flushing an empty
  accumulator never applies. Runs of separators and trailing whitespace
  push empty strings into the results, and `is_valid()` does not filter
  them. `Host  alpha   beta ` parses as `{ 'alpha', '', 'beta' }`.
- In `parse_value()`, the condition reduces to `chr == '"' and quoted`.
  `quoted` starts false and only that branch sets it, so it can never
  become true: quotes are never recognised and are inserted literally,
  and the unterminated-quote check is unreachable.

Solution:
Compare `#val` instead. Add a test for repeated and trailing separators.

AI-assisted

runtime/lua/vim/net/_ssh.lua

@@ -84,7 +84,7 @@ function M.parse_ssh_config(text)
       if escaped then
         table.insert(val, chr == '"' and chr or '\\' .. chr)
         escaped = false
-      elseif chr == '"' and (val == {} or quoted) then
+      elseif chr == '"' and (#val == 0 or quoted) then
         quoted = not quoted
       elseif chr == '\\' then
         escaped = true
@@ -127,7 +127,7 @@ function M.parse_ssh_config(text)
       elseif quoted then
         table.insert(val, chr)
       elseif chr:match('[ \t=]') then
-        if val ~= {} then
+        if #val > 0 then
           table.insert(results, vim.trim(table.concat(val)))
           val = {}
         end
@@ -143,7 +143,7 @@ function M.parse_ssh_config(text)
       error('Unexpected line break at line ' .. line)
     end
 
-    if val ~= {} then
+    if #val > 0 then
       table.insert(results, vim.trim(table.concat(val)))
     end