Streams: Consistent behaviour when reading from stream with error.

The streaming operator doesn't short-circuit, consider the following
snippet:

    void foo(InputStream& stream) {
        int a, b;
        stream >> a >> b;
    }

If the first read fails, the second is called regardless. It should be
well defined what happens in this case: nothing.

Libraries/LibCore/FileStream.h

@@ -65,6 +65,9 @@ public:
 
     size_t read(Bytes bytes) override
     {
+        if (has_any_error())
+            return 0;
+
         auto nread = m_buffered.bytes().copy_trimmed_to(bytes);
 
         m_buffered.bytes().slice(nread, m_buffered.size() - nread).copy_to(m_buffered);