patch 9.0.1051: after a failed CTRL-W ] next command splits window

Problem:    After a failed CTRL-W ] next command splits window.
Solution:   Reset postponed_split. (Rob Pilling, closes #11698)

src/window.c

@@ -559,6 +559,7 @@ newwindow:
 		// Execute the command right here, required when "wincmd ]"
 		// was used in a function.
 		do_nv_ident(Ctrl_RSB, NUL);
+		postponed_split = 0;
 		break;
 
 // edit file name under cursor in a new window
@@ -674,6 +675,7 @@ wingotofile:
 			// Execute the command right here, required when
 			// "wincmd g}" was used in a function.
 			do_nv_ident('g', xchar);
+			postponed_split = 0;
 			break;
 
 		    case 'f':	    // CTRL-W gf: "gf" in a new tab page