🐞 frontend: Fix editor buglets (#116)

* Highlight first, not last error token in line
* Fix empty/delete-all editor bug

This merges the following commits:
* frontend: Fix empty editor bug
* frontend: Highlight first, not last error in line

     frontend/index.js              | 4 +++-
     frontend/module/yace-editor.js | 4 +++-
     2 files changed, 6 insertions(+), 2 deletions(-)

Pull-Request: #116

Author: juliaogris

frontend/index.js

@@ -120,7 +120,9 @@ function jsError(ptr, len) {
   const errorLines = {}
   for (const err of errs) {
     const g = err.match(re).groups
-    errorLines[g.line] = { col: g.col, text: lines[g.line - 1] }
+    if (!errorLines[g.line]) {
+      errorLines[g.line] = { col: g.col, text: lines[g.line - 1] }
+    }
     msgs += `line ${g.line}: ${g.msg}\n`
   }
   const output = document.querySelector("#console")

frontend/module/yace-editor.js

@@ -81,7 +81,9 @@ export default class Yace {
     ) {
       return
     }
-    this.value = value || this.value
+    if (value != null && value != undefined) {
+      this.value = value
+    }
     this.errorLines = errorLines || this.errorLines
     const lines = this.value.split("\n")
     this.updateErrorLines(lines)