patch 8.1.0651: :args \"foo works like :args without argument

Problem:    :args \"foo works like :args without argument.
Solution:   Fix check for empty argument. (closes #3728)

src/ex_cmds2.c

@@ -2738,7 +2738,7 @@ ex_args(exarg_T *eap)
 	    alist_new();
     }
 
-    if (!ends_excmd(*eap->arg))
+    if (*eap->arg != NUL)
     {
 	/*
 	 * ":args file ..": define new argument list, handle like ":next"

src/testdir/test_arglist.vim

@@ -217,6 +217,12 @@ func Test_list_arguments()
   %argdelete
 endfunc
 
+func Test_args_with_quote()
+  args \"foobar
+  call assert_equal('"foobar', argv(0))
+  %argdelete
+endfunc
+
 " Test for 0argadd and 0argedit
 " Ported from the test_argument_0count.in test script
 func Test_zero_argadd()

src/version.c

@@ -799,6 +799,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    651,
 /**/
     650,
 /**/