Fixed bug that broke installing without kwargs

[TylerSchroederWM]

In all available documentation sources, the CLI for ssb-plugins is given as

sbot plugins.install plugin-name

However, on Ubuntu 20.04.41 and with muxrpcli 3.1.2, this will throw an error of the form

/usr/local/lib/node_modules/ssb-server/node_modules/muxrpcli/index.js:123
      throw err
      ^
TypeError: Cannot set property 'module' of undefined
    at Object.install (/usr/local/lib/node_modules/ssb-server/node_modules/ssb-plugins/index.js:117:23)
    at Object.hooked (/usr/local/lib/node_modules/ssb-server/node_modules/hoox/index.js:10:15)
    at Object.localCall (/usr/local/lib/node_modules/ssb-server/node_modules/muxrpc/local-api.js:31:29)
    at Object.<anonymous> (/usr/local/lib/node_modules/ssb-server/node_modules/muxrpc/local-api.js:37:22)
    at PacketStreamSubstream.stream.read (/usr/local/lib/node_modules/ssb-server/node_modules/muxrpc/stream.js:69:23)
    at PacketStream._onstream (/usr/local/lib/node_modules/ssb-server/node_modules/packet-stream/index.js:228:11)
    at PacketStream.write (/usr/local/lib/node_modules/ssb-server/node_modules/packet-stream/index.js:135:41)
    at /usr/local/lib/node_modules/ssb-server/node_modules/muxrpc/pull-weird.js:56:15
    at /usr/local/lib/node_modules/ssb-server/node_modules/pull-stream/sinks/drain.js:24:37
    at /usr/local/lib/node_modules/ssb-server/node_modules/pull-goodbye/node_modules/pull-stream/throughs/filter.js:17:11

This is because install/uninstall commands assume _opts is not undefined, while on muxrpcli 3.1.2, _opts will be undefined if no keyword args are passed.

The problem is fixed simply by setting _opts to an empty object if it is undefined.

[TylerSchroederWM]

It appears that this simple fix breaks plugins further down the line. Looking further into it.

[TylerSchroederWM]

On further investigation, the breaks in the second post were caused by the npm version not having this commit pushed yet.

The initial fix works fine on a fresh install of ssb-server with the most recent version of ssb-plugins pulled.