patch 8.1.0511: ml_get error when calling a function with a range

Problem:    ml_get error when calling a function with a range.
Solution:   Don't position the cursor after the last line.

src/testdir/test_functions.vim

@@ -1119,3 +1119,22 @@ func Test_func_sandbox()
   call assert_fails('call Fsandbox()', 'E48:')
   delfunc Fsandbox
 endfunc
+
+func EditAnotherFile()
+  let word = expand('<cword>')
+  edit Xfuncrange2
+endfunc
+
+func Test_func_range_with_edit()
+  " Define a function that edits another buffer, then call it with a range that
+  " is invalid in that buffer.
+  call writefile(['just one line'], 'Xfuncrange2')
+  new
+  call setline(1, range(10))
+  write Xfuncrange1
+  call assert_fails('5,8call EditAnotherFile()', 'E16:')
+
+  call delete('Xfuncrange1')
+  call delete('Xfuncrange2')
+  bwipe!
+endfunc

src/userfunc.c

@@ -3149,6 +3149,13 @@ ex_call(exarg_T *eap)
     {
 	if (!eap->skip && eap->addr_count > 0)
 	{
+	    if (lnum > curbuf->b_ml.ml_line_count)
+	    {
+		// If the function deleted lines or switched to another buffer
+		// the line number may become invalid.
+		EMSG(_(e_invrange));
+		break;
+	    }
 	    curwin->w_cursor.lnum = lnum;
 	    curwin->w_cursor.col = 0;
 #ifdef FEAT_VIRTUALEDIT

src/version.c

@@ -792,6 +792,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    511,
 /**/
     510,
 /**/