Handle Spiget api errors

so plugins with special characters such as "InvSee++" don't crash pluGET
due to unexpected Spiget api data structure response:
{'error': '', 'msg': ''}

Root cause may be special chracters not being URL-escaped by Spiget

src/plugin/plugin_updatechecker.py

@@ -520,6 +520,13 @@ def search_plugin_spiget(plugin_file: str, plugin_file_name: str, plugin_file_ve
     """
     url = f"https://api.spiget.org/v2/search/resources/{plugin_file_name}?field=name&sort=-downloads"
     plugin_list = api_do_request(url)
+    
+    # Handle failed api request
+    """{'error': 'Unexpected Exception', 'msg': 'Unexpected Exception. Please report this to https://github.com/SpiGetOrg/api.spiget.org/issues'}"""
+    if "error" in plugin_list:
+        print(f"Spiget error occurred whilst searching for plugin '{plugin_file}': {plugin_list['msg']}")
+        return plugin_list['msg']
+    else:
         plugin_file_version2 = plugin_file_version
         for i in range(4):
             if i == 1: