fix: HTTP power meter: retrieve multiple JSON paths

if only a single request was made (switch "Individual HTTP requests per
phase" is off), the user could still enable phase 2 and phase 3 config
and configure a respective JSON path. however, the value was never
extracted from the successful HTTP request for phase 1.

closes #637.

src/HttpPowerMeter.cpp

@@ -38,6 +38,13 @@ bool HttpPowerMeterClass::updateValues()
                 MessageOutput.printf("%s\r\n", httpPowerMeterError);
                 return false;
             }
+            continue;
+        }
+
+        if(!tryGetFloatValueForPhase(i, phaseConfig.JsonPath)) {
+            MessageOutput.printf("[HttpPowerMeter] Getting the power of phase %d (from JSON fetched with Phase 1 config) failed.\r\n", i + 1);
+            MessageOutput.printf("%s\r\n", httpPowerMeterError);
+            return false;
         }
     }
     return true;