fix: mark hash params as read when hash value is empty

An improvement for #144 when hash param is empty on first read

cosmoz-data-nav.js

@@ -978,15 +978,22 @@ class CosmozDataNav extends hauntedPolymer('haunted', useDataNav)(PolymerElement
 		}
 
 		const path = ['_routeHashParams', hashParam],
-			hashValue = this.get(path),
-			selection = this.items.findIndex(i => this._getItemId(i) === hashValue);
+			hashValue = this.get(path);
+
+		if (!hashValue) {
+			this._readFromHashOnce = true;
+			return;
+		}
+
+		const selection = this.items.findIndex(i => this._getItemId(i) === hashValue);
 
 		if (selection < 0 || selection === this.selected) {
 			return;
 		}
 		this._readFromHashOnce = true;
 		this.selected = selection;
 		return true;
+
 	}
 
 }