Revert setting speed to 0 when importing polars

include/Polar.h

@@ -113,8 +113,8 @@ class Polar
         SailingWindSpeed(double nVW) : VW(nVW) {}
 
         float VW;
-        std::vector<float> speeds; // by degree_count
-        std::vector<float> orig_speeds; // by degree_count, from polar file
+        std::vector<float> speeds;      // by degree_count
+        std::vector<float> orig_speeds; // by degree_count, from polar file.
         SailingVMG VMG;
     }; // num_wind_speeds
     bool VMGAngle(SailingWindSpeed &ws1, SailingWindSpeed &ws2, float VW, float &W);

src/Polar.cpp

@@ -304,7 +304,7 @@ bool Polar::Open(const wxString &filename, wxString &message)
                                         "To specify interpolated, leave blank values.\n"
                                         "To specify course as 'invalid' use 0.0 rather than 0\n"));
                         warn_zeros = true;
-                        s = 0;
+                        // Intentionally set s = NAN. This is to indicate the boat speed is unknow.
                     } else if(*token) {
                         s = strtod(token, 0);
                         if(s < .05)