add getVarbitCount and warn instead of throw when varb doesnt exist

runelite-api/src/main/java/net/runelite/api/Client.java

@@ -809,6 +809,11 @@ public interface Client extends GameShell
 	 */
 	void setVarbitValue(int[] varps, int varbit, int value);
 
+	/**
+	 * @return the total number of VarbitDefinition
+	 */
+	int getVarbitCount();
+
 	/**
 	 * Gets the widget flags table.
 	 *