redshift-gtk: Ignore exception in termwait when child is gone

The termwait method is used to wait until the child process has
quit. Previously this would fail with an exception if the child
has already quit. This is now ignored.

src/redshift-gtk/statusicon.py

@@ -357,8 +357,12 @@ class RedshiftStatusIcon(object):
         return True
 
     def termwait(self):
-        os.kill(self.process[0], signal.SIGINT)
-        os.waitpid(self.process[0], 0)
+        try:
+            os.kill(self.process[0], signal.SIGINT)
+            os.waitpid(self.process[0], 0)
+        except ProcessLookupError:
+            # Process has apparently already disappeared
+            pass
 
 
 def run():