Do not crash on UTF-8 decode errors (#423)

This PR implements a fix suggested in #407.

There are also other UTF-8 related issues:
#130
#347
#292

gdbgui/server/ptylib.py

@@ -76,7 +76,7 @@ def read(self) -> Optional[str]:
         if data_to_read:
             try:
                 response = os.read(self.stdout, self.max_read_bytes).decode()
-            except OSError:
+            except (OSError, UnicodeDecodeError):
                 return None
             return response
         return None