fix(functions): if schema.properties is empty, do not send schema (CopilotC-Nvim#1211)

This breaks stuff especially with github mcp server

Signed-off-by: Tomas Slusny <slusnucky@gmail.com>

Author: deathbeam

lua/CopilotChat/functions.lua

@@ -48,10 +48,16 @@ local function filter_schema(tbl)
     return tbl
   end
 
+  if utils.empty(tbl.properties) then
+    return nil
+  end
+
   local result = {}
   for k, v in pairs(tbl) do
-    if type(v) ~= 'function' and k ~= 'examples' then
-      result[k] = type(v) == 'table' and filter_schema(v) or v
+    if not utils.empty(v) then
+      if type(v) ~= 'function' and k ~= 'examples' then
+        result[k] = type(v) == 'table' and filter_schema(v) or v
+      end
     end
   end
   return result