http: Check fread() result to avoid warning.

This will cause the length not to match the result if it happens, but the
client should interpret that as a server error.

Also a similar error in headless.

Core/WebServer.cpp

@@ -163,7 +163,8 @@ static void RegisterDiscHandlers(http::Server *http, std::unordered_map<std::str
 			char *buf = new char[CHUNK_SIZE];
 			for (s64 pos = 0; pos < len; pos += CHUNK_SIZE) {
 				s64 chunklen = std::min(len - pos, (s64)CHUNK_SIZE);
-				fread(buf, chunklen, 1, fp);
+				if (fread(buf, chunklen, 1, fp) != 1)
+					break;
 				request.Out()->Push(buf, chunklen);
 			}
 			fclose(fp);

headless/StubHost.cpp

@@ -71,7 +71,9 @@ void HeadlessHost::SendDebugScreenshot(const u8 *pixbuf, u32 w, u32 h)
 		FILE *bmp = File::OpenCFile(comparisonScreenshot_, "rb");
 		if (bmp)
 		{
-			fread(&header, sizeof(header), 1, bmp);
+			if (fread(&header, sizeof(header), 1, bmp) != 1) {
+				SendOrCollectDebugOutput("Failed to read original screenshot header.\n");
+			}
 			fclose(bmp);
 		}