Bugfix #21262: Loading Alpha 0 project crash in Alpha 1

Old temp-pointers for File Browser instances were not being cleared on file load, resulting in crashes when trying to free temp screen layouts that contained file browser instance data.

source/blender/blenloader/intern/readfile.c

@@ -5125,6 +5125,18 @@ static void direct_link_screen(FileData *fd, bScreen *sc)
 				//	cl->line= newdataadr(fd, cl->line);
 				
 			}
+			else if(sl->spacetype==SPACE_FILE) {
+				SpaceFile *sfile= (SpaceFile *)sl;
+				
+				/* this sort of info is probably irrelevant for reloading...
+				 * plus, it isn't saved to files yet!
+				 */
+				sfile->folders_prev= sfile->folders_next= NULL;
+				sfile->files= NULL;
+				sfile->layout= NULL;
+				sfile->op= NULL;
+				sfile->params= NULL;
+			}
 		}
 		
 		sa->actionzones.first= sa->actionzones.last= NULL;

source/blender/blenloader/intern/writefile.c

@@ -2080,6 +2080,7 @@ static void write_screens(WriteData *wd, ListBase *scrbase)
 						write_curvemapping(wd, sima->cumap);
 				}
 				else if(sl->spacetype==SPACE_IMASEL) {
+					// XXX: depreceated... do we still want to keep this?
 					writestruct(wd, DATA, "SpaceImaSel", 1, sl);
 				}
 				else if(sl->spacetype==SPACE_TEXT) {