fix copy+paste mistakes in commit 9b0e5c555c0f (CVE-2019-7637 fix):

http://hg.libsdl.org/SDL/rev/9b0e5c555c0f made copy+paste mistakes which
resulted in windows versions failing to set video mode.

Author: sezero

src/video/gapi/SDL_gapivideo.c

@@ -733,7 +733,7 @@ SDL_Surface *GAPI_SetVideoMode(_THIS, SDL_Surface *current,
 	video->w = gapi->w = width;
 	video->h = gapi->h = height;
 	video->pitch = SDL_CalculatePitch(video); 
-	if (!current->pitch) {
+	if (!video->pitch) {
 		return(NULL);
 	}
 

src/video/windib/SDL_dibvideo.c

@@ -675,7 +675,7 @@ SDL_Surface *DIB_SetVideoMode(_THIS, SDL_Surface *current,
 	video->w = width;
 	video->h = height;
 	video->pitch = SDL_CalculatePitch(video);
-	if (!current->pitch) {
+	if (!video->pitch) {
 		return(NULL);
 	}
 

src/video/windx5/SDL_dx5video.c

@@ -1127,7 +1127,7 @@ SDL_Surface *DX5_SetVideoMode(_THIS, SDL_Surface *current,
 		video->w = width;
 		video->h = height;
 		video->pitch = SDL_CalculatePitch(video);
-		if (!current->pitch) {
+		if (!video->pitch) {
 			return(NULL);
 		}