add missing map init from `application.init()`

[hfoxy]

Description

Fixes a bug where registering events would cause a nil map assignment panic.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration using wails doctor.

• [ ] Windows
• [x] macOS
• [ ] Linux

Test Configuration

# System
┌──────────────────────────────┐
| Name          | MacOS        |
| Version       | 14.4.1       |
| ID            | 23E224       |
| Branding      | Sonoma       |
| Platform      | darwin       |
| Architecture  | arm64        |
| Apple Silicon | true         |
| CPU           | Apple M2 Pro |
| CPU           | Unknown      |
| GPU           | Unknown      |
| Memory        | Unknown      |
└──────────────────────────────┘

# Build Environment
┌─────────────────────────────────────────────────────────────────────────────────────────────────┐
| Wails CLI      | v3.0.0-alpha.4                                                                 |
| Go Version     | go1.22.2                                                                       |
| Revision       | b050a07362c84be5f7223fd79e31084746850b54                                       |
| Modified       | false                                                                          |
| -buildmode     | exe                                                                            |
| -compiler      | gc                                                                             |
| CGO_CFLAGS     |                                                                                |
| CGO_CPPFLAGS   |                                                                                |
| CGO_CXXFLAGS   |                                                                                |
| CGO_ENABLED    | 1                                                                              |
| CGO_LDFLAGS    |                                                                                |
| DefaultGODEBUG | httplaxcontentlength=1,httpmuxgo121=1,tls10server=1,tlsrsakex=1,tlsunsafeekm=1 |
| GOARCH         | arm64                                                                          |
| GOOS           | darwin                                                                         |
| vcs            | git                                                                            |
| vcs.modified   | false                                                                          |
| vcs.revision   | b050a07362c84be5f7223fd79e31084746850b54                                       |
| vcs.time       | 2024-04-22T02:44:10Z                                                           |
└─────────────────────────────────────────────────────────────────────────────────────────────────┘

# Dependencies
┌───────────────────────────┐
| Xcode cli tools | 2406    |
| npm             | 10.4.0  |
| *NSIS           | v3.10   |
└─ * - Optional Dependency ─┘

Checklist:

• [x] I have updated website/src/pages/changelog.mdx with details of this PR
• [x] My code follows the general coding style of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes