Fix segmentation fault when column name is NULL.

So, some columns (ex: SECATTR) can be sortable now.

ColumnsPanel.c

@@ -135,15 +135,6 @@ ColumnsPanel* ColumnsPanel_new(Settings* settings) {
    return this;
 }
 
-int ColumnsPanel_fieldNameToIndex(const char* name) {
-   for (int j = 1; j <= Platform_numberOfFields; j++) {
-      if (String_eq(name, Process_fields[j].name)) {
-         return j;
-      }
-   }
-   return -1;
-}
-
 void ColumnsPanel_update(Panel* super) {
    ColumnsPanel* this = (ColumnsPanel*) super;
    int size = Panel_size(super);

ColumnsPanel.h

@@ -23,8 +23,6 @@ extern const PanelClass ColumnsPanel_class;
 
 ColumnsPanel* ColumnsPanel_new(Settings* settings);
 
-int ColumnsPanel_fieldNameToIndex(const char* name);
-
 void ColumnsPanel_update(Panel* super);
 
 #endif

htop.c

@@ -129,7 +129,15 @@ static CommandLineSettings parseArguments(int argc, char** argv) {
                }
                exit(0);
             }
-            flags.sortKey = ColumnsPanel_fieldNameToIndex(optarg);
+            flags.sortKey = -1;
+            for (int j = 1; j < Platform_numberOfFields; j++) {
+               if (Process_fields[j].name == NULL)
+                  continue;
+               if (String_eq(optarg, Process_fields[j].name)) {
+                  flags.sortKey = j;
+                  break;
+               }
+            }
             if (flags.sortKey == -1) {
                fprintf(stderr, "Error: invalid column \"%s\".\n", optarg);
                exit(1);