Empty use abort declaration triggers asc assertion since 0.9.3

[jeffcharles]

When I call asc with --use abort= as documented in https://docs.assemblyscript.org/details/debugging#overriding-abort, I see:

➜  mar16 npx asc src/mar16.ts -b build/mar16.wasm --sourceMap --validate --optimize --use abort= --runtime none --lib=node_modules 
ERROR: AssertionError: assertion failed
    at assert (/Users/jeffreycharles/scripts/mar16/node_modules/assemblyscript/dist/webpack:/assemblyscript/std/portable/index.js:184:9)
    at g.initialize (/Users/jeffreycharles/scripts/mar16/node_modules/assemblyscript/dist/webpack:/assemblyscript/src/program.ts:1007:22)
    at Object.t.initializeProgram (/Users/jeffreycharles/scripts/mar16/node_modules/assemblyscript/dist/webpack:/assemblyscript/src/index.ts:221:11)
    at /Users/jeffreycharles/scripts/mar16/node_modules/assemblyscript/cli/asc.js:595:22
    at measure (/Users/jeffreycharles/scripts/mar16/node_modules/assemblyscript/cli/asc.js:1103:3)
    at Object.main (/Users/jeffreycharles/scripts/mar16/node_modules/assemblyscript/cli/asc.js:594:26)
    at /Users/jeffreycharles/scripts/mar16/node_modules/assemblyscript/bin/asc:21:47

It looks like src/program.ts on line 1007 has let name = assert(globalAliases.get(alias)); and globalAliases has a key called abort which has a value of '' which is falsey in JavaScript which causes the assert to fire.

[DuncanUszkay1]

Going to look into this