remove image markdown when upload image fail

Author: thaichors3000

src/commands/default-commands/save-image-command.tsx

@@ -78,8 +78,7 @@ export const saveImageCommand: Command = {
           end: initialState.selection.start + placeHolder.length
         });
 
-        const realImageMarkdown = `${breaksBefore}![image](${imageUrl})`;
-
+        const realImageMarkdown = imageUrl ? `${breaksBefore}![image](${imageUrl})` : "";
         const selectionDelta = realImageMarkdown.length - placeHolder.length;
 
         textApi.replaceSelection(realImageMarkdown);