Don't add analyze plugin when buildOptions == nil

[mateusz834]

This should fix a panic when using the --analyze CLI option.
Examples:

[mateusz@arch esbuild (fix-analyze-cli-panic)]$ ./esbuild --analyze
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x2f8 pc=0x8a5f09]

goroutine 1 [running]:
github.com/evanw/esbuild/pkg/cli.addAnalyzePlugin(...)
        /home/mateusz/code/esbuild/pkg/cli/cli_impl.go:1107
github.com/evanw/esbuild/pkg/cli.runImpl({0xc000024070, 0x1, 0x1})
        /home/mateusz/code/esbuild/pkg/cli/cli_impl.go:1145 +0x409
github.com/evanw/esbuild/pkg/cli.Run(...)
        /home/mateusz/code/esbuild/pkg/cli/cli.go:31
main.main.func1({0x0?, 0xc00004c638?}, {0xc000024070?, 0x1, 0x1}, {0x0?, 0x0?}, {0x0, 0x0}, 0xc00013fea0, ...)
        /home/mateusz/code/esbuild/cmd/esbuild/main.go:361 +0x4cf
main.main()
        /home/mateusz/code/esbuild/cmd/esbuild/main.go:363 +0x9ac

[mateusz@arch esbuild (fix-analyze-cli-panic)]$ ./esbuild index.js --outfile=out.js --analyze --bundle --unknownOpt
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x2f8 pc=0x8a5f09]

goroutine 1 [running]:
github.com/evanw/esbuild/pkg/cli.addAnalyzePlugin(...)
        /home/mateusz/code/esbuild/pkg/cli/cli_impl.go:1107
github.com/evanw/esbuild/pkg/cli.runImpl({0xc0000241f0, 0x5, 0x5})
        /home/mateusz/code/esbuild/pkg/cli/cli_impl.go:1145 +0x409
github.com/evanw/esbuild/pkg/cli.Run(...)
        /home/mateusz/code/esbuild/pkg/cli/cli.go:31
main.main.func1({0x0?, 0xc00004e638?}, {0xc0000241f0?, 0x5, 0x5}, {0x0?, 0x0?}, {0x0, 0x0}, 0xc00017fea0, ...)
        /home/mateusz/code/esbuild/cmd/esbuild/main.go:361 +0x4cf
main.main()
        /home/mateusz/code/esbuild/cmd/esbuild/main.go:363 +0x9ac