Strip empty ProseMirror text nodes from third-party list documents

The third-party list template emitted a text node for every optional
field even when the value was empty, producing `{"text":""}` nodes that
violate the ProseMirror schema and make Tiptap refuse to render the
document with "Empty text nodes are not allowed".

Add a `default` template helper and substitute "—" for empty values in
third_party_list.json.tmpl, and add a migration that rewrites existing
document_versions.content to drop any empty text nodes (per-row safe,
preserves marks/attrs/ordering, leaves updated_at untouched).

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/coredata/migrations/20260520T113200Z.sql

@@ -0,0 +1,86 @@
+-- Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+-- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+-- AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+-- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+-- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+-- OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+-- PERFORMANCE OF THIS SOFTWARE.
+
+-- Strip empty ProseMirror text nodes from document_versions.content.
+-- Empty text nodes are invalid per the ProseMirror schema and cause Tiptap
+-- to refuse rendering the document with "Empty text nodes are not allowed".
+
+CREATE OR REPLACE FUNCTION pg_temp.strip_empty_text_nodes(input jsonb) RETURNS jsonb
+LANGUAGE plpgsql IMMUTABLE AS $$
+DECLARE
+    item     jsonb;
+    new_arr  jsonb := '[]'::jsonb;
+    out_obj  jsonb;
+BEGIN
+    IF jsonb_typeof(input) = 'object' THEN
+        out_obj := input;
+        IF input ? 'content' AND jsonb_typeof(input->'content') = 'array' THEN
+            FOR item IN SELECT * FROM jsonb_array_elements(input->'content') LOOP
+                IF item->>'type' = 'text'
+                   AND (item->>'text' IS NULL OR item->>'text' = '') THEN
+                    CONTINUE;
+                END IF;
+                new_arr := new_arr || jsonb_build_array(pg_temp.strip_empty_text_nodes(item));
+            END LOOP;
+            out_obj := jsonb_set(out_obj, '{content}', new_arr);
+        END IF;
+        RETURN out_obj;
+    ELSIF jsonb_typeof(input) = 'array' THEN
+        FOR item IN SELECT * FROM jsonb_array_elements(input) LOOP
+            new_arr := new_arr || jsonb_build_array(pg_temp.strip_empty_text_nodes(item));
+        END LOOP;
+        RETURN new_arr;
+    ELSE
+        RETURN input;
+    END IF;
+END;
+$$;
+
+DO $$
+DECLARE
+    r           record;
+    cleaned     jsonb;
+    cleaned_txt text;
+    scanned     integer := 0;
+    updated     integer := 0;
+    skipped     integer := 0;
+BEGIN
+    FOR r IN
+        SELECT dv.id, dv.content
+        FROM document_versions dv
+        JOIN documents d ON d.id = dv.document_id
+        WHERE d.write_mode = 'GENERATED'
+          AND (dv.content LIKE '%"text":""%' OR dv.content LIKE '%"text": ""%')
+    LOOP
+        scanned := scanned + 1;
+        BEGIN
+            cleaned := pg_temp.strip_empty_text_nodes(r.content::jsonb);
+        EXCEPTION WHEN OTHERS THEN
+            skipped := skipped + 1;
+            RAISE NOTICE 'document_versions.id=% skipped: %', r.id, SQLERRM;
+            CONTINUE;
+        END;
+
+        cleaned_txt := cleaned::text;
+        IF cleaned_txt IS DISTINCT FROM r.content THEN
+            UPDATE document_versions
+            SET content = cleaned_txt
+            WHERE id = r.id;
+            updated := updated + 1;
+        END IF;
+    END LOOP;
+
+    RAISE NOTICE 'strip_empty_text_nodes: scanned=% updated=% skipped=%',
+        scanned, updated, skipped;
+END $$;