Fix lineAtHeight when asking past end, but last line is collapsed

Author: marijnh

lib/codemirror.js

@@ -3063,7 +3063,7 @@ window.CodeMirror = (function() {
       else if (line > last) { line = last; end = true; }
       var lineObj = getLine(this.doc, line);
       return intoCoordSystem(this, getLine(this.doc, line), {top: 0, left: 0}, mode || "page").top +
-        (end ? lineObj.height : 0);
+        (end ? this.doc.height - heightAtLine(this, lineObj) : 0);
     },
 
     defaultTextHeight: function() { return textHeight(this.display); },