Fix warnings added in 8d9a0e85bd.

src/tools/msvc/Solution.pm

@@ -162,11 +162,13 @@ sub GenerateFiles
 		  || confess "Could not open pg_config.h.win32\n";
 		open(O, ">src\\include\\pg_config.h")
 		  || confess "Could not write to pg_config.h\n";
+		my $extraver = $self->{options}->{extraver};
+		$extraver = '' unless defined $extraver;
 		while (<I>)
 		{
-			s{PG_VERSION "[^"]+"}{PG_VERSION "$self->{strver}$self->{options}->{extraver}"};
+			s{PG_VERSION "[^"]+"}{PG_VERSION "$self->{strver}$extraver"};
 			s{PG_VERSION_NUM \d+}{PG_VERSION_NUM $self->{numver}};
-			s{PG_VERSION_STR "[^"]+"}{__STRINGIFY(x) #x\n#define __STRINGIFY2(z) __STRINGIFY(z)\n#define PG_VERSION_STR "PostgreSQL $self->{strver}$self->{options}->{extraver}, compiled by Visual C++ build " __STRINGIFY2(_MSC_VER) ", $bits-bit"};
+			s{PG_VERSION_STR "[^"]+"}{__STRINGIFY(x) #x\n#define __STRINGIFY2(z) __STRINGIFY(z)\n#define PG_VERSION_STR "PostgreSQL $self->{strver}$extraver, compiled by Visual C++ build " __STRINGIFY2(_MSC_VER) ", $bits-bit"};
 			print O;
 		}
 		print O "#define PG_MAJORVERSION \"$self->{majorver}\"\n";