Get connectToSerialPort to rethrow its serial port opening error to h…

…opefully improve error message generation on linux

- Changed error handling in `connectToSerialport.js` to throw exceptions instead of returning null on failure.

src/renderer/utils/connectToSerialport.js

@@ -126,6 +126,6 @@ export const connectToSerialport = async (targetVid, targetPid) => {
     return focus;
   } catch (e) {
     logger.error("Failed to open serial port", e);
-    return null;
+    throw e;
   }
 };