fix: add default empty table for state.source

Add nil check for state.source by providing empty table as default value to
prevent errors when source is not initialized. This ensures the code handles
undefined source gracefully.

lua/CopilotChat/init.lua

@@ -274,7 +274,7 @@ local function resolve_embeddings(prompt, config)
   local embeddings = utils.ordered_map()
   for _, context_data in ipairs(contexts) do
     local context_value = M.config.contexts[context_data.name]
-    for _, embedding in ipairs(context_value.resolve(context_data.input, state.source)) do
+    for _, embedding in ipairs(context_value.resolve(context_data.input, state.source or {})) do
       if embedding then
         embeddings:set(embedding.filename, embedding)
       end
@@ -460,7 +460,7 @@ local function trigger_complete()
         local value_str = tostring(value)
         vim.api.nvim_buf_set_text(bufnr, row - 1, col, row - 1, col, { value_str })
         vim.api.nvim_win_set_cursor(0, { row, col + #value_str })
-      end, state.source)
+      end, state.source or {})
     end
 
     return