kjs - pcre: Fix crash if regexp is invalid.

If the regular expression is invalid and pcre2_compile ends with error,
match_data will remain uninitialized, which in turn leads to crash on
pcre2_match_data_free in RegExp destructor.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit 3150a4542f)

kjs/regexp.cpp

@@ -149,6 +149,7 @@ RegExp::RegExp(const UString &p, int f)
     pcre2_get_error_message(errorCode, errorMsg, sizeof(errorMsg));
     fprintf(stderr, "KJS: pcre_compile() failed with '%s'\n", errorMsg);
 #endif
+    match_data = nullptr;
     valid = false;
     return;
   }