feat(index): add validation for pattern

lua/hlslens/index.lua

@@ -13,8 +13,20 @@ local function find_hls_qfnr()
     return 0
 end
 
+local function valid_pat(pat)
+    if pat == '' then
+        return false
+    end
+    for g in pat:gmatch('.?/') do
+        if g ~= [[\/]] then
+            return false
+        end
+    end
+    return true
+end
+
 function M.build_index(pattern)
-    if pattern == '' then
+    if not valid_pat(pattern) then
         return
     end
 
@@ -55,6 +67,11 @@ function M.build_index(pattern)
         end
     end
 
+    -- don't waste the memory :)
+    if fn.getqflist({size = 0}).size > 100000 then
+        return
+    end
+
     local pos_list = ok and vim.tbl_map(function(item)
         return {item.lnum, item.col}
     end, fn.getqflist()) or {}