Fix empty string matching bug.

ChangeLog

@@ -151,6 +151,10 @@ overflows.
 38. The table entry for \l in EBCDIC environments was incorrect, leading to its
 being treated as a literal 'l' instead of causing an error.
 
+39. If a non-capturing group containing a conditional group that could match
+an empty string was repeated, it was not identified as matching an empty string 
+itself. For example: /^(?:(?(1)x|)+)+$()/.
+
 
 Version 10.10 06-March-2015
 ---------------------------

src/pcre2_compile.c

@@ -1338,7 +1338,7 @@ for (code = first_significant_code(code + PRIV(OP_lengths)[*code], TRUE);
   if (c == OP_BRA  || c == OP_BRAPOS ||
       c == OP_CBRA || c == OP_CBRAPOS ||
       c == OP_ONCE || c == OP_ONCE_NC ||
-      c == OP_COND)
+      c == OP_COND || c == OP_SCOND)
     {
     BOOL empty_branch;
     if (GET(code, 1) == 0) return TRUE;    /* Hit unclosed bracket */

testdata/testinput2

@@ -4325,4 +4325,6 @@ a random value. /Ix
 
 /(?<=|(\,\$(?73591620449005828816)\xa8.{7}){6}\x09)/
 
+/^(?:(?(1)x|)+)+$()/B
+
 # End of testinput2 

testdata/testoutput2

@@ -14452,4 +14452,22 @@ Failed: error 162 at offset 4: subpattern name expected
 /(?<=|(\,\$(?73591620449005828816)\xa8.{7}){6}\x09)/
 Failed: error 161 at offset 32: number is too big
 
+/^(?:(?(1)x|)+)+$()/B
+------------------------------------------------------------------
+        Bra
+        ^
+        SBra
+        SCond
+      1 Cond ref
+        x
+        Alt
+        KetRmax
+        KetRmax
+        $
+        CBra 1
+        Ket
+        Ket
+        End
+------------------------------------------------------------------
+
 # End of testinput2