fix software update button

TODO.md

@@ -2,7 +2,6 @@
 
 - add faq entry about range and antennas and rain
 - first message sent is still doubled for some people
-- disable software update button after update finishes
 - let users set arbitrary params in android
 - add a low level settings screen (let user change any of the RadioConfig parameters)
 

app/src/main/java/com/geeksville/mesh/ui/SettingsFragment.kt

@@ -484,10 +484,12 @@ class SettingsFragment : ScreenFragment("Settings"), Logging {
                     updateProgressBar.progress = service.updateStatus
                     delay(2000) // Only check occasionally
                 }
+
+                val isSuccess = (service.updateStatus == -1)
                 scanStatusText.text =
-                    if (service.updateStatus == -1) "Update successful" else "Update failed"
+                    if (isSuccess) "Update successful" else "Update failed"
                 updateProgressBar.isEnabled = false
-                updateFirmwareButton.isEnabled = true
+                updateFirmwareButton.isEnabled = !isSuccess
             }
         }
     }