Fix allocate zero size memory warning (#1143)
Fix allocate zero size memory warning (#1143)

Fix allocate zero size memory warning reported by wasm_runtime_malloc
when allocating the import fun pointers if the import func count is 0:
    `warning: wasm_runtime_malloc with size zero`
bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime,bytecodealliance/wasm-micro-runtime