Fix crash when null is used for an array in .cdb.json

Fixes #298

app/flatpages/help/package_config.md

@@ -65,7 +65,7 @@ It should be a JSON dictionary with one or more of the following optional keys:
 * `forums`: forum topic ID.
 * `video_url`: URL to a video.
 
-Use `null` to unset fields where relevant.
+Use `null` or `[]` to unset fields where relevant.
 
 Example:
 

app/logic/package_validator.py

@@ -0,0 +1,39 @@
+from collections import namedtuple
+from typing import List
+
+from flask_babel import lazy_gettext
+from sqlalchemy import and_, or_
+
+from app.models import Package, PackageType, PackageState, PackageRelease
+
+ValidationError = namedtuple("ValidationError", "status message")
+
+
+def validate_package_for_approval(package: Package) -> List[ValidationError]:
+	retval: List[ValidationError] = []
+
+	normalised_name = package.getNormalisedName()
+	if package.type != PackageType.MOD and Package.query.filter(
+			and_(Package.state == PackageState.APPROVED,
+				 or_(Package.name == normalised_name,
+					 Package.name == normalised_name + "_game"))).count() > 0:
+		retval.append(("danger", lazy_gettext("A package already exists with this name. Please see Policy and Guidance 3")))
+
+	if package.releases.filter(PackageRelease.task_id.is_(None)).count() == 0:
+		retval.append(("danger", lazy_gettext("A release is required before this package can be approved.")))
+		# Don't bother validating any more until we have a release
+		return retval
+
+	missing_deps = package.getMissingHardDependenciesQuery().all()
+	if len(missing_deps) > 0:
+		retval.append(("danger", lazy_gettext(
+			"The following hard dependencies need to be added to ContentDB first: %(deps)s", deps=missing_deps)))
+
+	if (package.type == package.type.GAME or package.type == package.type.TXP) and \
+		package.screenshots.count() == 0:
+		retval.append(("danger", lazy_gettext("You need to add at least one screenshot.")))
+
+	if "Other" in package.license.name or "Other" in package.media_license.name:
+		retval.append(("info", lazy_gettext("Please wait for the license to be added to CDB.")))
+
+	return retval

app/logic/packages.py

@@ -150,7 +150,7 @@ def do_edit_package(user: User, package: Package, was_new: bool, was_web: bool,
 	if "tags" in data:
 		old_tags = list(package.tags)
 		package.tags.clear()
-		for tag_id in data["tags"]:
+		for tag_id in (data["tags"] or []):
 			if is_int(tag_id):
 				tag = Tag.query.get(tag_id)
 			else:
@@ -173,7 +173,7 @@ def do_edit_package(user: User, package: Package, was_new: bool, was_web: bool,
 
 	if "content_warnings" in data:
 		package.content_warnings.clear()
-		for warning_id in data["content_warnings"]:
+		for warning_id in (data["content_warnings"] or []):
 			if is_int(warning_id):
 				package.content_warnings.append(ContentWarning.query.get(warning_id))
 			else: