patch 9.0.0188: strange effects when using "text_align" with non-zero column

Problem:    Strange effects when using virtual text with "text_align" and
            non-zero column. (Martin Tournoij)
Solution:   Give an error. (closes #10888)

src/errors.h

@@ -3313,4 +3313,6 @@ EXTERN char e_cmdline_window_already_open[]
 #ifdef FEAT_PROP_POPUP
 EXTERN char e_cannot_use_negative_id_after_adding_textprop_with_text[]
 	INIT(= N_("E1293: Cannot use a negative id after adding a textprop with text"));
+EXTERN char e_can_only_use_text_align_when_column_is_zero[]
+	INIT(= N_("E1294: Can only use text_align when column is zero"));
 #endif

src/testdir/test_textprop.vim

@@ -2530,6 +2530,8 @@ func Test_props_with_text_after()
 
   call StopVimInTerminal(buf)
   call delete('XscriptPropsWithTextAfter')
+
+  call assert_fails('call prop_add(1, 2, #{text: "yes", text_align: "right", type: "some"})', 'E1294:')
 endfunc
 
 func Test_props_with_text_after_below_trunc()

src/textprop.c

@@ -488,6 +488,11 @@ prop_add_common(
 
 	    if (p == NULL)
 		goto theend;
+	    if (start_col != 0)
+	    {
+		emsg(_(e_can_only_use_text_align_when_column_is_zero));
+		goto theend;
+	    }
 	    if (STRCMP(p, "right") == 0)
 		flags |= TP_FLAG_ALIGN_RIGHT;
 	    else if (STRCMP(p, "below") == 0)

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    188,
 /**/
     187,
 /**/