Fix empty record creation failing in PostgresProvider

lib/pg.provider.js

@@ -558,11 +558,17 @@ class PostgresProvider extends StorageProvider {
         values.push(id.toString());
       }
       fields = fields.map(escapeIdentifier);
-      const createQuery =
-        `INSERT INTO ${escapeIdentifier(category)} ` +
-        `(${fields.join(', ')})` +
-        ` VALUES (${generateQueryParams(fields.length)})` +
-        ' RETURNING "Id"';
+
+      let createQuery = `INSERT INTO ${escapeIdentifier(category)} `;
+      if (fields.length !== 0) {
+        createQuery +=
+          `(${fields.join(', ')})` +
+          ` VALUES (${generateQueryParams(fields.length)})`;
+      } else {
+        createQuery += 'DEFAULT VALUES';
+      }
+      createQuery += ' RETURNING "Id"';
+
       const res = await client.query(createQuery, values);
       return res.rows[0].Id;
     };

test/fixtures/pg-test-schemas/Local.category

@@ -0,0 +1,3 @@
+Local({
+  SomeData: { domain: 'Nomen' },
+})

test/fixtures/pg-test-schemas/OptionalRegistry.category

@@ -0,0 +1,3 @@
+Registry({
+  SomeData: { domain: 'Nomen' },
+})

test/pg.js

@@ -100,6 +100,12 @@ metatests.test(
           }
         });
 
+        test.test('empty create on local category', async test => {
+          const id = await provider.create('Local', {});
+          test.assert(id);
+          test.end();
+        });
+
         test.test('create on global category', async test => {
           const { category, value } = record;
           const id = await provider.create(category, value);
@@ -122,6 +128,12 @@ metatests.test(
           }
         });
 
+        test.test('empty create on global category', async test => {
+          const id = await provider.create('OptionalRegistry', {});
+          test.assert(id);
+          test.end();
+        });
+
         test.test('create on ignored category', async test => {
           try {
             await provider.create('TestMemory', {