Remove redundant NULL checks before free()/delete (#2184)

Remove redundant NULL checks before free()/delete

The ISO C and C++ standards guarantee that it's safe to call these
on a NULL pointer, so it's not necessary for the calling code to
also check.

Fixes https://sourceforge.net/p/swig/feature-requests/70/

Doc/Manual/SWIG.html

@@ -1470,14 +1470,14 @@ SWIG generates the following code:
 <pre>
 /* C mode */
 void foo_set(char *value) {
-  if (foo) free(foo);
+  free(foo);
   foo = (char *) malloc(strlen(value)+1);
   strcpy(foo, value);
 }
 
 /* C++ mode.  When -c++ option is used */
 void foo_set(char *value) {
-  if (foo) delete [] foo;
+  delete [] foo;
   foo = new char[strlen(value)+1];
   strcpy(foo, value);
 }
@@ -2635,8 +2635,7 @@ char *Foo_name_get(Foo *obj) {
 }
 
 char *Foo_name_set(Foo *obj, char *c) {
-  if (obj-&gt;name)
-    free(obj-&gt;name);
+  free(obj-&gt;name);
   obj-&gt;name = (char *) malloc(strlen(c)+1);
   strcpy(obj-&gt;name, c);
   return obj-&gt;name;

Doc/Manual/Tcl.html

@@ -2811,9 +2811,7 @@ used as a <tt>char **</tt> object.
 
 // This gives SWIG some cleanup code that will get called after the function call
 %typemap(freearg) char ** {
-  if ($1) {
-    free($1);
-  }
+  free($1);
 }
 
 // Now a test functions

Doc/Manual/Typemaps.html

@@ -3103,7 +3103,7 @@ as shown.   To work with heap allocated data, the following technique can be use
   }
 }
 %typemap(freearg) float value[ANY] {
-  if ($1) free($1);
+  free($1);
 }
 </pre>
 </div>
@@ -3556,7 +3556,7 @@ maps perform the conversion described for the above example:
 }
 
 %typemap(freearg) (int argc, char *argv[]) {
-  if ($2) free($2);
+  free($2);
 }
 
 /* Required for C++ method overloading */