fix the crash with opening the file

Author: Disinterpreter

amx-test/testgm.amx

@@ -20,10 +20,18 @@ public OnGameModeInit()
 	print("");
 
 	new File:f = fopen("file.txt", io_read);
-	new buffer[512];
-	fread(f, buffer, sizeof(buffer));
-	fclose(f);
-	printf("%s", buffer);
+    if (f == File:0)
+    {
+        printf("There is a problem with openning the file.");
+    }
+    else
+    {
+		new buffer[512];
+		fread(f, buffer, sizeof(buffer));
+		fclose(f);
+		printf("%s", buffer);
+        fclose(f);
+    }
 
 	AddPlayerClass(0, 1958.3783, 1343.1572, 15.3746, 269.1425, 0, 0, 0, 0, 0, 0);
 	SetRuleValue("nya", "test");