patch 8.2.2774: Vim9: cannot import an existing name even when using "as"

Problem:    Vim9: cannot import an existing name even when using "as".
Solution:   Do not check for an existing name when using "as". (closes #8113)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index d9ae4ff..2f2fc9c 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -1280,6 +1280,8 @@
 
   var import_lines =<< trim END
     vim9script
+    var one = 'notused'
+    var yes = 777
     import one as thatOne from './XexportAs'
     assert_equal(1, thatOne)
     import yes as yesYes from './XexportAs'
diff --git a/src/version.c b/src/version.c
index 113ba8f..5d26348 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2774,
+/**/
     2773,
 /**/
     2772,
diff --git a/src/vim9script.c b/src/vim9script.c
index 796b7d1..583a8d4 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -600,7 +600,8 @@
 	    }
 	    else
 	    {
-		if (check_defined(name, len, cctx, FALSE) == FAIL)
+		if (as_name == NULL
+			      && check_defined(name, len, cctx, FALSE) == FAIL)
 		    goto erret;
 
 		imported = new_imported(gap != NULL ? gap