Update Charges API to Allow Valid Empty Response

API should fail gracefully if an empty response is sent.
Example reason: an API consumer should be able to traverse the pages until empty data is returned.

Note: currently this is not possible, since a generic error will be thrown if the data set is empty (including on a fresh install of TeslaMate) or if there is an invalid charge in the response. It's impossible to know if all data points were traversed or if an error exists on a single charge (See: https://github.com/tobiasehlert/teslamateapi/issues/43)

src/v1_TeslaMateAPICarsCharges.go

@@ -179,6 +179,11 @@ func TeslaMateAPICarsChargesV1(c *gin.Context) {
 	if err != nil {
 		log.Fatal(err)
 	}
+	
+	// if no errors, but ChargeData is empty, return a valid response with an empty set
+	if len(ChargeData) == 0 {
+		ValidResponse = true
+	}
 
 	//
 	// build the data-blob