Fixed issue LMMS#5734 (FreeBoy Division by zero).

Added comments and used more descriptive variable names for noise
channel initialization block.

Also indented the nested for loop to improve code clarity.
The reasons for doing this can be found in this answer:
https://softwareengineering.stackexchange.com/a/362796

plugins/FreeBoy/FreeBoy.cpp

@@ -364,25 +364,33 @@ void FreeBoyInstrument::playNote( NotePlayHandle * _n,
 
 	if( tfp == 0 )
 	{
+		// Initialize noise channel...
 		//PRNG Frequency = (1048576 Hz / (ratio + 1)) / 2 ^ (shiftclockfreq + 1)
-		char sopt=0;
-		char ropt=1;
-		float fopt = 524288.0 / ( ropt * pow( 2.0, sopt + 1.0 ) );
-		float f;
-		for ( char s=0; s<16; s++ )
-		for ( char r=0; r<8; r++ ) {
-			f = 524288.0 / ( r * pow( 2.0, s + 1.0 ) );
-			if( fabs( freq-fopt ) > fabs( freq-f ) ) {
-				fopt = f;
-				ropt = r;
-				sopt = s;
+		char clock_freq = 0;
+		char div_ratio = 1;
+		float closest_freq = 524288.0 / ( div_ratio * pow( 2.0, clock_freq + 1.0 ) );
+		// This nested for loop iterates over all possible combinations of clock frequency and dividing
+		// ratio and chooses the combination whose resulting frequency is closest to the note frequency
+		for ( char s = 0; s < 16; s++ )
+		{
+			for ( char r = 0 ; r < 8; r++ )
+			{
+				float r_val = (r == 0 ? 0.5 : r);
+				float f = 524288.0 / ( r_val * pow( 2.0, s + 1.0 ) );
+				if( fabs( freq - closest_freq ) > fabs( freq - f ) )
+				{
+					closest_freq = f;
+					div_ratio = r;
+					clock_freq = s;
+				}
 			}
 		}
-		data = sopt;
+
+		data = clock_freq;
 		data = data << 1;
 		data += m_ch4ShiftRegWidthModel.value();
 		data = data << 3;
-		data += ropt;
+		data += div_ratio;
 		papu->write_register( fakeClock(),  0xff22, data );
 
 		//channel 4 init