Ensure getInstallProperties always returns a value

With React Query 4+ a query function must always either return a value
or throw an error. The install properties getter was previously returning
undefined which meant React Query 3 would keep using the placeholder data.
That's no longer the case so we have to return the default in this case.

src/api/index.js

@@ -107,6 +107,10 @@ export async function getInstallProperties() {
     data = await get(uri);
   } catch (error) {
     if (error?.response?.status === 404) {
+      // eslint-disable-next-line no-console
+      console.warn(
+        'Install properties not found, setting client-mode defaults'
+      );
       data = {
         dashboardNamespace: 'N/A',
         dashboardVersion: 'kubectl-proxy-client',
@@ -116,6 +120,13 @@ export async function getInstallProperties() {
         triggersNamespace: 'Unknown',
         triggersVersion: 'Unknown'
       };
+    } else {
+      // eslint-disable-next-line no-console
+      console.error(
+        'Failed loading install properties, setting read-only default',
+        error
+      );
+      data = { isReadOnly: true };
     }
   }
   return data;

src/api/index.test.js

@@ -483,7 +483,7 @@ describe('getInstallProperties', () => {
       http.get(/\/properties$/, () => new HttpResponse(null, { status: 500 }))
     );
     const properties = await API.getInstallProperties();
-    expect(properties).toBeUndefined();
+    expect(properties).toEqual({ isReadOnly: true });
   });
 });