fix for [#28201] blender crashes when "mpeg" selected

2 changes
- When writing OGG only allow Theora encoding, this fixes the crash.
- When setting the MPEG preset, dont allow the 'Codec' to be left as Theora, this is just confusing.

* note that this is highly confusing for users and devs - there are 4 places to set the codec/format, with both python and C presets :S.

source/blender/blenkernel/intern/writeffmpeg.c

@@ -658,10 +658,12 @@ static int start_ffmpeg_impl(struct RenderData *rd, int rectx, int recty, Report
 	switch(ffmpeg_type) {
 	case FFMPEG_AVI:
 	case FFMPEG_MOV:
-	case FFMPEG_OGG:
 	case FFMPEG_MKV:
 		fmt->video_codec = ffmpeg_codec;
 		break;
+	case FFMPEG_OGG:
+		fmt->video_codec = CODEC_ID_THEORA;
+		break;
 	case FFMPEG_DV:
 		fmt->video_codec = CODEC_ID_DVVIDEO;
 		break;
@@ -1310,6 +1312,9 @@ void ffmpeg_verify_image_type(RenderData *rd)
 			/* Don't set preset, disturbs render resolution.
 			 * ffmpeg_set_preset(rd, FFMPEG_PRESET_DVD); */
 		}
+		if(rd->ffcodecdata.type == FFMPEG_OGG) {
+			rd->ffcodecdata.type = FFMPEG_MPEG2;
+		}
 
 		audio= 1;
 	}