Minor code cleanup based on valgrind analysis

NEWS

@@ -18,6 +18,8 @@
 - Make explicit casts in gptcurses.cc to eliminate compiler warnings about
   mis-matched types in printw() statements.
 
+- Minor code cleanup based on valgrind analysis.
+
 - In previous versions, rEFInd accepted only integer values for partition
   start points, end points, and sizes, and it interpreted decimal values
   incorrectly. That is, if you typed "+9.5G" as the partition end point,

gpt.cc

@@ -80,6 +80,7 @@ GPTData::GPTData(void) {
    beQuiet = 0;
    whichWasUsed = use_new;
    mainHeader.numParts = 0;
+   mainHeader.firstUsableLBA = 0;
    mainHeader.lastUsableLBA = 0;
    numParts = 0;
    SetGPTSize(NUM_GPT_ENTRIES);