Remove useless checks for NULL before freeing

This patch has been generated by the following Coccinelle semantic
patch:

// Remove useless checks for NULL before freeing
//
// free (NULL) is a no-op, so there is no need to avoid it

@@
expression E;
@@
+ free (E);
+ E = NULL;
- if (unlikely (E != NULL)) {
-   free(E);
(
-   E = NULL;
|
-   E = 0;
)
   ...
- }

@@
expression E;
type T;
@@
+ free ((T) E);
+ E = NULL;
- if (unlikely (E != NULL)) {
-   free((T) E);
(
-   E = NULL;
|
-   E = 0;
)
   ...
- }

@@
expression E;
@@
+ free (E);
- if (unlikely (E != NULL)) {
-   free (E);
- }

@@
expression E;
type T;
@@
+ free ((T) E);
- if (unlikely (E != NULL)) {
-   free ((T) E);
- }

Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/program/program.c

@@ -382,8 +382,7 @@ _mesa_delete_program(struct gl_context *ctx, struct gl_program *prog)
    if (prog == &_mesa_DummyProgram)
       return;
 
-   if (prog->String)
-      free(prog->String);
+   free(prog->String);
 
    if (prog->Instructions) {
       _mesa_free_instructions(prog->Instructions, prog->NumInstructions);