Correctly detect missing clutter file

inputs.cc

@@ -3,6 +3,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <math.h>
+#include <errno.h>
 #include "common.h"
 #include "main.hh"
 
@@ -22,9 +23,8 @@ int loadClutter(char *filename, double radius, struct site tx)
 	char * pch;
 	FILE *fd;
 
-	fd = fopen(filename, "rb");
-
-	if (fd != NULL) {
+	if( (fd = fopen(filename, "rb")) == NULL)
+		return errno;
 
 	if (fgets(line, 19, fd) != NULL) {
 		pch = strtok (line," ");
@@ -120,7 +120,7 @@ int loadClutter(char *filename, double radius, struct site tx)
 			fprintf(stderr, "Clutter error @ x %d y %d\n", x, y);
 		}//if
 	}//for
-	}
+
 	fclose(fd);
 	return 0;
 }

main.cc

@@ -1042,7 +1042,7 @@ int main(int argc, char *argv[])
 	int x, y, z = 0, min_lat, min_lon, max_lat, max_lon,
 	    rxlat, rxlon, txlat, txlon, west_min, west_max,
 	    nortRxHin, nortRxHax, propmodel, knifeedge = 0, ppa =
-	    0, normalise = 0, haf = 0, pmenv = 1, lidar=0, cropped;
+	    0, normalise = 0, haf = 0, pmenv = 1, lidar=0, cropped, result;
 
 	bool use_threads = true;
 
@@ -1797,7 +1797,10 @@ int main(int argc, char *argv[])
 		Clutter tiles cover 16 x 12 degs but we only need a fraction of that area.
 		Limit by max_range / miles per degree (at equator)
 		*/
-		loadClutter(clutter_file,max_range/45,tx_site[0]); 
+		if( (result = loadClutter(clutter_file,max_range/45,tx_site[0])) != 0 ){
+			fprintf(stderr, "Error, invalid or clutter file not found\n");
+			return result;
+		}
 	}
 
 	if (ppa == 0) {