Fix sketch <base> when usaved, handle nonstring messages

Author: catarak

client/modules/IDE/components/Editor.jsx

@@ -253,7 +253,7 @@ class Editor extends React.Component {
           if (consoleEvent.method === 'error') {
             // It doesn't work if you create a new Error, but this works
             // LOL
-            const errorObj = { stack: consoleEvent.data[0] };
+            const errorObj = { stack: consoleEvent.data[0].toString() };
             StackTrace.fromError(errorObj).then((stackLines) => {
               this.props.expandConsole();
               const line = stackLines.find(

client/modules/Preview/EmbedFrame.jsx

@@ -214,7 +214,7 @@ function injectLocalFiles(files, htmlFile, options) {
   const sketchDoc = parser.parseFromString(htmlFile.content, 'text/html');
 
   const base = sketchDoc.createElement('base');
-  base.href = `${window.origin}${basePath}/`;
+  base.href = `${window.origin}${basePath}${basePath.length > 1 && '/'}`;
   sketchDoc.head.appendChild(base);
 
   resolvePathsForElementsWithAttribute('src', sketchDoc, resolvedFiles);