presets: Avoid string conversion on bad "name" type

Source/cmCMakePresetsErrors.cxx

@@ -42,7 +42,10 @@ std::string getPresetName(cmJSONState* state)
 {
   Json::Value const* preset = getPreset(state);
   if (preset && preset->isMember("name")) {
-    return preset->operator[]("name").asString();
+    Json::Value const& name = preset->operator[]("name");
+    if (name.isConvertibleTo(Json::ValueType::stringValue)) {
+      return name.asString();
+    }
   }
   return "";
 }

Tests/Fuzzing/corpus/presets/name-list.json

@@ -0,0 +1,11 @@
+{
+    "version":6,
+    "configurePresets": [
+        {
+            "name": [],
+            "cacheVariables": {
+                "": {}
+            }
+        }
+    ]
+}