Don't swallow errors when resolving arguments (elastic#648)

Fixes https://github.com/elastic/kibana-canvas/issues/278.

This PR simply bubbles up errors that come as a result of attempting to resolve the argument subexpressions.

common/interpreter/interpret.js

@@ -158,6 +158,7 @@ export function interpretProvider(config) {
       return argAsts.map(argAst => {
         return async (ctx = context) => {
           const newContext = await interpret(argAst, ctx);
+          if (getType(newContext) === 'error') throw newContext.error;
           return cast(newContext, argDefs[argName].types);
         };
       });