What year did maggs magnificent mild win a gold medal in the mild and porter category at the siba south east region beer competition?
CREATE TABLE table_51059 (
    "Year" real,
    "Beer Name" text,
    "Prize" text,
    "Category" text,
    "Competition" text
)
SELECT AVG("Year") FROM table_51059 WHERE "Beer Name" = 'maggs magnificent mild' AND "Prize" = 'gold medal' AND "Category" = 'mild and porter' AND "Competition" = 'siba south east region beer competition'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What year did maggs magnificent mild win a gold medal in the mild and porter category at the siba south east region beer competition? ### Input: CREATE TABLE table_51059 (
    "Year" real,
    "Beer Name" text,
    "Prize" text,
    "Category" text,
    "Competition" text
) ### Response: SELECT AVG("Year") FROM table_51059 WHERE "Beer Name" = 'maggs magnificent mild' AND "Prize" = 'gold medal' AND "Category" = 'mild and porter' AND "Competition" = 'siba south east region beer competition'