Bug 1784588 - Fix SplitDriverVersion when the string has less than 4 numbers. r=aosmond

Differential Revision: https://phabricator.services.mozilla.com/D154897

widget/GfxDriverInfo.h

@@ -460,6 +460,9 @@ inline bool SplitDriverVersion(const char* aSource, char* aAStr, char* aBStr,
   // Add last terminator.
   MOZ_ASSERT(destIdx < 4 && destPos <= 4);
   dest[destIdx][destPos] = 0;
+  for (int unusedDestIdx = destIdx + 1; unusedDestIdx < 4; unusedDestIdx++) {
+    dest[unusedDestIdx][0] = 0;
+  }
 
   if (destIdx != 3) {
     return false;