Fix fastboot issue and clear error text at the right time

Author: tsterbak

openandroidinstaller/tooling.py

@@ -102,6 +102,7 @@ def adb_reboot_bootloader(bin_path: Path) -> Union[str, bool]:
     """Reboot the device into bootloader and return success."""
     for line in run_command("adb reboot bootloader", bin_path):
         yield line
+    sleep(1)
 
 
 @add_logging("Rebooting device into download mode with adb.")

openandroidinstaller/views/step_view.py

@@ -195,6 +195,8 @@ def call_to_phone(self, e, command: str):
 
         Some parts of the command are changed by placeholders.
         """
+        # clean the previous error display
+        self.error_text.value = ""
         # disable the call button while the command is running
         self.call_button.disabled = True
         # reset the progress indicators