Fixed narrowing warning when Rx sample size is 16 bits

sdrbase/dsp/dspdevicemimoengine.cpp

@@ -453,12 +453,11 @@ void DSPDeviceMIMOEngine::workSamplesSource(SampleVector& data, unsigned int iBe
                     begin,
                     begin,
                     [this](Sample& a, const Sample& b) -> Sample {
-                        int den = m_sumIndex + 1; // at each stage scale sum by n/n+1 and input by 1/n+1
-                        int nom = m_sumIndex;     // so that final sum is scaled by N (number of channels)
-                        return Sample{
-                            a.real()/den + nom*(b.real()/den),
-                            a.imag()/den + nom*(b.imag()/den)
-                        };
+                        FixReal den = m_sumIndex + 1; // at each stage scale sum by n/n+1 and input by 1/n+1
+                        FixReal nom = m_sumIndex;     // so that final sum is scaled by N (number of channels)
+                        FixReal x = a.real()/den + nom*(b.real()/den);
+                        FixReal y = a.imag()/den + nom*(b.imag()/den);
+                        return Sample{x, y};
                     }
                 );
             }