libdtterm: Resolve uninitialized warnings

cde/lib/DtTerm/Term/TermBuffer.c

@@ -984,8 +984,8 @@ _DtTermBufferErase
     DtEraseMode eraseSwitch
 )
 {
-    short  startCol;
-    short  lastCol;
+    short  startCol = 0;
+    short  lastCol = 0;
     
     switch(eraseSwitch)
     {

cde/lib/DtTerm/Term/TermParse.c

@@ -529,6 +529,8 @@ _DtTermEraseDisplay(Widget w)    /* ED CSIpJ */
     case 2: 
       eraseMode = eraseBuffer;
       break ; 
+    default:
+      return;
    }
    _DtTermFuncEraseInDisplay(w, (int)eraseMode, fromParser);
   vtw->term.tpd->cursorRow = row;
@@ -746,6 +748,9 @@ _DtTermEraseInLine(Widget w)  /* EL  ESC[pK */
       eraseMode = eraseLine;
       break;
 
+    default:
+      return;
+
   }
   _DtTermFuncEraseInLine(w, (int)eraseMode, fromParser);
 }