Fix #8592 - Presence of 'ROWS <n_limit>' causes garbage in error message when string conversion problem raises.

Author: asfernandes

src/jrd/cvt2.cpp

@@ -221,11 +221,16 @@ static int cmp_numeric_string(const dsc* arg1, const dsc* arg2, Firebird::Decima
 	Decimal128 buffer;		// enough to fit any required data
 	SSHORT scale = 0;
 	UCHAR* text = arg2->dsc_address;
+	USHORT textLen = TEXT_LEN(arg2);
+
 	if (arg2->dsc_dtype == dtype_varying)
+	{
 		text += sizeof(USHORT);
+		textLen -= sizeof(USHORT);
+	}
 
 	dsc num2;
-	num2.dsc_dtype = CVT_get_numeric(text, TEXT_LEN(arg2), &scale, &buffer);
+	num2.dsc_dtype = CVT_get_numeric(text, textLen, &scale, &buffer);
 	num2.dsc_address = (UCHAR*)&buffer;
 	num2.dsc_scale = scale;
 	num2.dsc_length = type_lengths[num2.dsc_dtype];