SDL_SetWindowTitle() should never set a NULL pointer for the title string.

Various backends reacted differently (or not at all) in the presence of a
NULL pointer. This simplifies things.

Fixes Bugzilla #2902.

src/video/SDL_video.c

@@ -1502,11 +1502,8 @@ SDL_SetWindowTitle(SDL_Window * window, const char *title)
         return;
     }
     SDL_free(window->title);
-    if (title && *title) {
-        window->title = SDL_strdup(title);
-    } else {
-        window->title = NULL;
-    }
+
+    window->title = SDL_strdup(title ? title : "");
 
     if (_this->SetWindowTitle) {
         _this->SetWindowTitle(_this, window);

src/video/cocoa/SDL_cocoawindow.m

@@ -1189,16 +1189,9 @@ Cocoa_SetWindowTitle(_THIS, SDL_Window * window)
 {
     NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
     NSWindow *nswindow = ((SDL_WindowData *) window->driverdata)->nswindow;
-    NSString *string;
-
-    if(window->title) {
-        string = [[NSString alloc] initWithUTF8String:window->title];
-    } else {
-        string = [[NSString alloc] init];
-    }
+    NSString *string = [[NSString alloc] initWithUTF8String:window->title];
     [nswindow setTitle:string];
     [string release];
-
     [pool release];
 }
 

src/video/directfb/SDL_DirectFB_WM.c

@@ -161,7 +161,7 @@ DirectFB_WM_RedrawLayout(_THIS, SDL_Window * window)
                y, w - 2 * d);
 
     /* Caption */
-    if (window->title) {
+    if (*window->title) {
         s->SetColor(s, COLOR_EXPAND(t->font_color));
         DrawCraption(_this, s, (x - w) / 2, t->top_size + d, window->title);
     }

src/video/windows/SDL_windowswindow.c

@@ -371,14 +371,8 @@ void
 WIN_SetWindowTitle(_THIS, SDL_Window * window)
 {
     HWND hwnd = ((SDL_WindowData *) window->driverdata)->hwnd;
-    LPTSTR title;
-
-    if (window->title) {
-        title = WIN_UTF8ToString(window->title);
-    } else {
-        title = NULL;
-    }
-    SetWindowText(hwnd, title ? title : TEXT(""));
+    LPTSTR title = WIN_UTF8ToString(window->title);
+    SetWindowText(hwnd, title);
     SDL_free(title);
 }
 

src/video/x11/SDL_x11window.c

@@ -658,39 +658,39 @@ X11_SetWindowTitle(_THIS, SDL_Window * window)
     Display *display = data->videodata->display;
     XTextProperty titleprop, iconprop;
     Status status;
-    const char *title = window->title;
+    const char *title = window->title ? window->title : "";
     const char *icon = NULL;
+    char *title_locale = NULL;
 
 #ifdef X_HAVE_UTF8_STRING
     Atom _NET_WM_NAME = data->videodata->_NET_WM_NAME;
     Atom _NET_WM_ICON_NAME = data->videodata->_NET_WM_ICON_NAME;
 #endif
 
-    if (title != NULL) {
-        char *title_locale = SDL_iconv_utf8_locale(title);
-        if (!title_locale) {
-            SDL_OutOfMemory();
-            return;
-        }
-        status = X11_XStringListToTextProperty(&title_locale, 1, &titleprop);
-        SDL_free(title_locale);
-        if (status) {
-            X11_XSetTextProperty(display, data->xwindow, &titleprop, XA_WM_NAME);
-            X11_XFree(titleprop.value);
-        }
+    title_locale = SDL_iconv_utf8_locale(title);
+    if (!title_locale) {
+        SDL_OutOfMemory();
+        return;
+    }
+
+    status = X11_XStringListToTextProperty(&title_locale, 1, &titleprop);
+    SDL_free(title_locale);
+    if (status) {
+        X11_XSetTextProperty(display, data->xwindow, &titleprop, XA_WM_NAME);
+        X11_XFree(titleprop.value);
+    }
 #ifdef X_HAVE_UTF8_STRING
-        if (SDL_X11_HAVE_UTF8) {
-            status =
-                X11_Xutf8TextListToTextProperty(display, (char **) &title, 1,
+    if (SDL_X11_HAVE_UTF8) {
+        status = X11_Xutf8TextListToTextProperty(display, (char **) &title, 1,
                                             XUTF8StringStyle, &titleprop);
-            if (status == Success) {
-                X11_XSetTextProperty(display, data->xwindow, &titleprop,
+        if (status == Success) {
+            X11_XSetTextProperty(display, data->xwindow, &titleprop,
                                  _NET_WM_NAME);
-                X11_XFree(titleprop.value);
-            }
+            X11_XFree(titleprop.value);
         }
-#endif
     }
+#endif
+
     if (icon != NULL) {
         char *icon_locale = SDL_iconv_utf8_locale(icon);
         if (!icon_locale) {