Retain filter state on unhandled keypress

src/nnn.c

@@ -3362,6 +3362,9 @@ nochange:
 
 			dentfree(dents);
 			return;
+		default:
+			if (sel && cfg.filtermode)
+				presel = FILTER;
 		} /* switch (sel) */
 
 		/* Screensaver */