raster: Fix uninitialized variable issue in o_var.c (#4005)

Fix uninitialized variable issue in o_var.c

Co-authored-by: Shubham Vasudeo Desai <[email protected]>

raster/r.statistics/o_var.c

@@ -17,7 +17,7 @@ int o_var(const char *basemap, const char *covermap, const char *outputmap,
 {
     struct Popen stats_child, reclass_child;
     FILE *stats, *reclass;
-    int first, i, count;
+    int first, i, count = 0;
     size_t mem;
     long basecat, covercat, catb, catc;
     double value, vari, x;