Leave more room for call frames and case data in PLASM

src/toolsrc/codegen.pla

@@ -589,7 +589,7 @@ def init_idglobal#0
     fixup_addr   = heapalloc(fixup_num*2)
     idglobal_tbl = heapalloc(globalbufsz)
     idlocal_tbl  = heapalloc(localbufsz)
-    codebufsz    = heapavail - 1024 // 2048
+    codebufsz    = heapavail - 2048
     codebuff     = heapalloc(codebufsz)
     codeptr      = codebuff
     lastglobal   = idglobal_tbl

src/toolsrc/parse.pla

@@ -805,6 +805,7 @@ def parse_stmnt
             caseval     = heapalloc(CASENUM*2)
             casetyp     = heapalloc(CASENUM*2)
             casetag     = heapalloc(CASENUM*2)
+            if not caseval or not casetyp or not casetag; exit_err(ERR_OVER); fin
             casecnt     = 0
             seq, cfnvals = parse_expr(NULL)
             if !seq; exit_err(ERR_INVAL|ERR_STATE); fin