Raise Msf::NoCompatiblePayloadError if generate_payload_exe fails

Most exploits don't check nil for generate_payload_exe, they just
assume they will always have a payload. If the method returns nil,
it ends up making debugging more difficult. Instead of checking nil
one by one, we just raise.

modules/exploits/multi/browser/java_atomicreferencearray.rb

@@ -138,13 +138,8 @@ class Metasploit3 < Msf::Exploit::Remote
         # NOTE: The EXE mixin automagically handles detection of arch/platform
         data = generate_payload_exe
 
-        if data
-          print_status("Generated executable to drop (#{data.length} bytes)." )
-          data = Rex::Text.to_hex( data, prefix="" )
-        else
-          print_error("Failed to generate the executable." )
-          return
-        end
+        print_status("Generated executable to drop (#{data.length} bytes)." )
+        data = Rex::Text.to_hex( data, prefix="" )
 
       end