fix: gracefully handle non-string operation summaries (via #5189)

test/e2e-cypress/static/documents/bugs/5188.yaml

@@ -0,0 +1,17 @@
+openapi: 3.0.0
+servers: []
+info:
+  description: sdf
+  version: "1.0.0"
+  title: Swagger Petstore
+paths:
+  /pet:
+    get:
+      tags:
+        - pet
+      summary: 
+        $ref: 
+      operationId: addPet
+      responses:
+        '405':
+          description: Invalid input

test/e2e-cypress/tests/bugs/5188.js

@@ -0,0 +1,10 @@
+describe("#5188: non-string operation summary value", () => {
+  it("should gracefully handle an object value for an operation summary", () => {
+    cy
+      .visit("?url=/documents/bugs/5188.yaml")
+      .get("#operations-pet-addPet")
+      .click()
+      .get(".opblock-summary-description")
+      .contains("[object Object]")
+    })
+})