Avoid crash because of GonvimResize arguments

Check arguments passed to GonvimResize to avoid crashes
because of wrong type (e.g. int64 instead of string) or incorrectly
formed (e.g. "" instead of "30x40").

Author: thjbdvlt

editor/editor.go

@@ -1103,11 +1103,18 @@ func (e *Editor) setWindowSizeFromOpts() {
 func (e *Editor) setWindowSize(s string) (int, int) {
 	var width, height int
 	var err error
-	width, err = strconv.Atoi(strings.SplitN(s, "x", 2)[0])
+
+	parsed_s := strings.SplitN(s, "x", 2)
+	if len(parsed_s) != 2 {
+		// TODO: Error message to user?
+		return 40, 30
+	}
+
+	width, err = strconv.Atoi(parsed_s[0])
 	if err != nil || width < 40 {
 		width = 40
 	}
-	height, err = strconv.Atoi(strings.SplitN(s, "x", 2)[1])
+	height, err = strconv.Atoi(parsed_s[1])
 	if err != nil || height < 30 {
 		height = 30
 	}

editor/workspace.go

@@ -1825,8 +1825,11 @@ func (ws *Workspace) handleGui(updates []interface{}) {
 		go setupGoneovimClipBoard(ws.nvim)
 	case "gonvim_uienter":
 	case "gonvim_resize":
-		width, height := editor.setWindowSize(updates[1].(string))
-		editor.window.Resize2(width, height)
+		arg, ok := updates[1].(string)
+		if ok {
+			width, height := editor.setWindowSize(arg)
+			editor.window.Resize2(width, height)
+		}
 	case "gonvim_fullscreen":
 		arg := 1
 		if len(updates) == 2 {