Use objectFlags&ObjectFlagsClassOrInterface guard instead of AsInterfaceType() != nil

Follow codebase convention of checking objectFlags before calling
AsInterfaceType(), matching how other callers protect against
non-interface types.

Agent-Logs-Url: https://github.com/microsoft/typescript-go/sessions/8ef1747a-398d-4fe9-a151-2b721a5249ce

Co-authored-by: jakebailey <5341706+jakebailey@users.noreply.github.com>

Author: Copilot

internal/checker/jsx.go

@@ -1041,7 +1041,7 @@ func (c *Checker) instantiateAliasOrInterfaceWithDefaults(managedSym *ast.Symbol
 			return c.getTypeAliasInstantiation(managedSym, args, nil)
 		}
 	}
-	if declaredManagedType.AsInterfaceType() != nil && len(declaredManagedType.AsInterfaceType().TypeParameters()) >= len(typeArguments) {
+	if declaredManagedType.objectFlags&ObjectFlagsClassOrInterface != 0 && len(declaredManagedType.AsInterfaceType().TypeParameters()) >= len(typeArguments) {
 		args := c.fillMissingTypeArguments(typeArguments, declaredManagedType.AsInterfaceType().TypeParameters(), len(typeArguments), inJavaScript)
 		return c.createTypeReference(declaredManagedType, args)
 	}