[bmv2] control block invocation bug

[smolkaj]

The following program compiles fine, but produces the error

terminate called after throwing an instance of 'std::runtime_error'
  what():  in Json::Value::operator[](char const*)const: requires objectValue
Aborted (core dumped)

at runtime when executed on simple_switch:

#include <core.p4>
#include <v1model.p4>
typedef standard_metadata_t std_meta_t;

struct H { }
struct M { }

control VerifyChecksumI(in H hdr, inout M meta) {
    apply { }
}

parser ParserI(packet_in b, out H parsedHdr, inout M meta,inout std_meta_t std_meta) {
    state start { transition accept; }
}

control ctrl(inout M meta) {
    apply { }
}

control IngressI(inout H hdr, inout M meta, inout std_meta_t std_meta) {

    ctrl() do_ctrl;

    apply {
        do_ctrl.apply(meta);
    }
}

control EgressI(inout H hdr, inout M meta, inout std_meta_t std_meta) {
    apply { }
} 

control ComputeChecksumI(inout H hdr, inout M meta) {
    apply { }
}
control DeparserI(packet_out b, in H hdr) {
    apply { }
}

V1Switch(ParserI(), VerifyChecksumI(), IngressI(), EgressI(), ComputeChecksumI(),
         DeparserI()) main;

[smolkaj]

fixed