Few form fixes

src/pages/admin/EventCreatePage.tsx

@@ -200,16 +200,18 @@ class EventCreatePage extends React.Component<EventCreatePageProps, EventCreateP
           type: ["array"],
           title: "Signup forms",
           items: {
+            type: ["number", "null"],
             // TODO: A bug here, DB must have at least one SignupForm, otherwise cannot submit
-            enum: [...signupForm.map(form => form.id)],
-            enumNames: [...signupForm.map(form => form.title)],
+            enum: signupForm.map(form => form.id),
+            enumNames: signupForm.map(form => form.title),
           },
           uniqueItems: true,
         },
         image: {
-          "type": ["string", "null"],
-          "format": formData.image ? "uri-reference" : "data-url",
-          "title": "Override tag icon with image"
+          type: ["string", "null"],
+          format: formData.image ? "uri-reference" : "data-url",
+          title: "Override tag icon with image",
+          default: ""
         },
         finnish_section_divider: {
           title: "Finnish",

src/pages/admin/SignupCreatePage.tsx

@@ -136,7 +136,7 @@ class SignupCreatePage extends React.Component<SignupCreatePageProps, SignupCrea
           default: true,
         },
         quota: {
-          type: "integer",
+          type: ["integer", "null"],
           title: "Quota",
           minimum: 0,
           default: null,