partially fix segfault when run with options but no input file

(caused by fclose()-ing an unopened file)

src/fix/main.c

@@ -167,8 +167,7 @@ int main(int argc, char *argv[])
 		strcat(filename, ".gb");
 
 	f = fopen(filename, "rb+");
-	if (!f)
-		FatalError("Unable to open file");
+        if( (f=fopen(filename,"rb+"))!=NULL ) {
 
 		/*
 		 * -d (Debug) option code
@@ -464,6 +463,9 @@ int main(int argc, char *argv[])
 		}
 
 		fclose(f);
+	} else {
+		FatalError("File '%s' not found",filename);
+	}
 
 	return (0);
 }