patch 8.0.0762: ml_get error with :psearch in buffer without a name

Problem:    ml_get error with :psearch in buffer without a name. (Dominique
            Pelle)
Solution:   Use the buffer number instead of the file name.  Check the cursor
            position.

Author: brammool

src/Makefile

@@ -2216,6 +2216,7 @@ test_arglist \
 	test_perl \
 	test_plus_arg_edit \
 	test_popup \
+	test_preview \
 	test_profile \
 	test_put \
 	test_python2 \

src/search.c

@@ -5425,14 +5425,15 @@ find_pattern_in_path(
 			if (g_do_tagpreview != 0)
 			{
 			    if (!GETFILE_SUCCESS(getfile(
-					    0, curwin_save->w_buffer->b_fname,
+					   curwin_save->w_buffer->b_fnum, NULL,
 						     NULL, TRUE, lnum, FALSE)))
 				break;	/* failed to jump to file */
 			}
 			else
 #endif
 			    setpcmark();
 			curwin->w_cursor.lnum = lnum;
+			check_cursor();
 		    }
 		    else
 		    {

src/testdir/Make_all.mak

@@ -175,6 +175,7 @@ NEW_TESTS = test_arabic.res \
 	    test_packadd.res \
 	    test_paste.res \
 	    test_perl.res \
+	    test_preview.res \
 	    test_profile.res \
 	    test_python2.res \
 	    test_python3.res \

src/testdir/test_preview.vim

@@ -0,0 +1,13 @@
+" Tests for the preview window
+
+func Test_Psearch()
+  " this used to cause ml_get errors
+  help
+  let wincount = winnr('$')
+  0f
+  ps.
+  call assert_equal(wincount + 1, winnr('$'))
+  pclose
+  call assert_equal(wincount, winnr('$'))
+  bwipe
+endfunc

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    762,
 /**/
     761,
 /**/