fix: completion dropdown must dupe completion data

Because it might be erased by the next completion response.

closes #477

src/buffer/reflow.zig

@@ -60,8 +60,16 @@ fn detect_prefix(text: []const u8) Prefix {
     var lines = std.mem.splitScalar(u8, text, '\n');
     const line1 = lines.next() orelse return .{};
     var prefix: []const u8 = line1;
-    while (lines.next()) |line|
+    var count: usize = 0;
+    while (lines.next()) |line| {
         prefix = lcp(prefix, line);
+        count += 1;
+    }
+    if (count < 1) return .{
+        .len = 0,
+        .first = &.{},
+        .continuation = &.{},
+    };
 
     if (line1.len > prefix.len + 2 and line1[prefix.len] == '-' and line1[prefix.len + 1] == ' ') {
         const first = line1[0 .. prefix.len + 2];

src/tui/mode/overlay/completion_dropdown.zig

@@ -36,6 +36,7 @@ pub const ValueType = struct {
     query: ?Buffer.Selection = null,
     last_query: ?[]const u8 = null,
     commands: command.Collection(cmds) = undefined,
+    data: []const u8 = &.{},
 };
 pub const defaultValue: ValueType = .{};
 
@@ -53,7 +54,9 @@ pub fn load_entries(self: *Type) !usize {
 
     self.value.cursor = self.value.editor.get_primary().cursor;
     self.value.query = null;
-    var iter: []const u8 = self.value.editor.completions.data.items;
+    self.allocator.free(self.value.data);
+    self.value.data = try self.allocator.dupe(u8, self.value.editor.completions.data.items);
+    var iter: []const u8 = self.value.data;
     while (iter.len > 0) {
         var cbor_item: []const u8 = undefined;
         if (!try cbor.matchValue(&iter, cbor.extract_cbor(&cbor_item))) return error.BadCompletion;
@@ -90,6 +93,7 @@ pub fn load_entries(self: *Type) !usize {
 }
 
 pub fn deinit(self: *Type) void {
+    self.allocator.free(self.value.data);
     if (self.value.last_query) |p| self.allocator.free(p);
     self.value.commands.deinit();
 }