fix(highlight): Do not let highlight exceed text range

Author: ajwild

src/highlight-support.js

@@ -45,8 +45,9 @@ const highlightSupport = {
       this.win
     )
 
-    const actualStartIndex = startIndex
-    const actualEndIndex = endIndex
+    // Do not let highlight exceed text range
+    const actualStartIndex = Math.min(Math.max(startIndex, 0), blockText.length - 1)
+    const actualEndIndex = Math.min(Math.max(endIndex, 1), blockText.length)
 
     // If text is provided then validate that it matches
     if (text) {
@@ -116,7 +117,7 @@ const highlightSupport = {
       if (position) res[highlightId] = position
     }
 
-    return res
+    return Object.keys(res).length > 0 ? res : undefined
   },
 
   extractMarkerNodePosition (editableHost, markers) {